I 


GIFT   OF 
MICHAEL  REE^E 


NOTES  ON  ASSAYING 


AND 


ASSAY  SCHEMES; 


BY 


PIERRE  DE  PEYSTER   RICKETTS,  E.  M.,  PH.  D 

Professor  of  Assaying,  School  of  Mines,  Columbia  College. 


FIFTEENTH  EDITION. 


UNIVERSITT 


SEVENTH   THOUSAND 

NEW  YORK 
JOHN  WILEY  &   SONS 

LONDON 

CHAPMAN  &  HALL,  LTD. 
1895 


i  l-C  ft 

Entered  according  to  Act  of  Congress,  in  the  year  1876,  by 

PIERRE  DE  P.  RICKETTS,  E.  M  ,  Ph.  D., 
in  the  office  of  the  Librarian  of  Congress,  at  Washington. 


Press  of  J.  J.  Little  &  Co., 
Astor  Place,  New  York- 


PEEFACE. 


WHEN  I  first  published  this  little  Manual  in  1876,  I  en- 
deavored to  prepare  it  in  such  a  way  that  it  would  prove 
serviceable  to  the  practical  as  well  as  the  scientific  student, 
and  for  that  reason  avoided  all  chemical  names  as  far  as 
possible,  giving  them,  when  necessary,  with  the  formulae  in 
parentheses,  and  in  the  Appendix  for  reference. 

x     y1     ""          '  # 

The  same  arrangement  has  been  retained  in  the  present 
enlarged  and  revised  edition,  the  success  of  the  first  having 
led  me  to  believe  that  the  plan  is  a  good  one. 

As  I  stated  in  my  first  preface,  the  work  embodies  the 
system  of  assaying  practiced  in  the  School  of  Mines  of 
Columbia  College,  organized  and  developed  by  Prof.  C. 
F.  CHANDLER  and  by  G.  M.  MILLEE,  E.  C.  H.  DAY,  F. 
PRIME,  JR.,  T.  M.  BLOSSOM,  E.  M.,  and  the  author  of  these 
notes,  who  have  successively  had  charge  of  the  assay  labo- 
ratory. The  system  of  assay  weights  employed,  was  de- 
vised by  Prof.  CHANDLER,  and  will  be  found  superior  to 
any  others  in  use,  in  the  saving  of  time  and  calculation. 

The  chapters  on  gold,  silver,  and  iron,  are  founded  on  the 
excellent  papers  published  by  Mr.  BLOSSOM,  in  the  Ameri- 
can Chemist  for  1870,  modifications  and  additions  having 
been  made  when  deemed  necessary.  Most  of  the  methods 


6  PEEFACE. 

given  have  been  tested  in  the  laboratory,  and  the  results 
appended  under  the  head  of  ' '  REMARKS  ; ' '  much  attention 
having  been  paid  to  the  various  details  peculiar  to  the 
West.  For  the  processes  for  testing  and  assaying  tellu- 
rides,  and  the  cupel  furnace  for  the  use  of  soft  coal,  I  am 
indebted  to  Mr.  W.  A.  HOOKEE.  Mr.  S.  G.  SACKETT  and 
Captain  C.  B.  DAHLGEEN  have  also  favored  me  with  much 
useful  information  as  to  Western  methods,  which  will,  I 
think,  be  found  useful  both  in  the  laboratory  and  field. 

In  the  Appendix,  the  chapter  on  blowpipe  analysis  has 
been  revised  and  enlarged,  and  an  outline  scheme  for  the 
assay  of  ores  added,  also  a  number  of  methods  for  testing 
gold  ores  and  alloys. 

The  advertisements  in  the  back  of  the  book  have  been 
retained  for  the  purpose  of  furnishing  a  guide  to  those  who 
wish  to  procure  assay  apparatus,  chemicals,  etc. ;  while 
the  lists  of  apparatus  have  been  revised,  prices  and  esti- 
mates being  given. 

PIERRE    DE  P.  RICKETTS. 

ASSAY  LABORATORY,  SCHOOL  OF  MINES, 
NEW  YORK,  June  1st,  1879. 


CONTENTS, 


PART   I. 

INTRODUCTION. —  APPARATUS.  —  REAGENTS  AND 
OPERATIONS. 


PART   II. 

DRY  OR  FIRE  ASSAYS. 


PART   III. 

WET  ASSAYS  OR  ANALYSES. 


PART  IV. 

TABLES  AND  REFERENCES. 


APPENDIX. 

MANIPULATION. — BLOWPIPE  ANALYSIS. — APPARATUS 
AND  REAGENTS.— SPECIAL  SCHEMES,  ETC. 


PART    FIRST. 

INTRODUCTION. 
BALANCES  AND  WEIGHTS. 
FURNACES  AND  FUELS. 
CRUCIBLES,  SCORIFIERS,  AND  CUPELS. 
LUTES,  CEMENTS,  AND  WASHES. 
TOOLS  AND  APPARATUS. 
REAGENTS  AND  CHEMICALS. 
PRELIMINARY  TESTING  OF  ORES. 
SAMPLING  AND  PULVERIZING. 
WEIGHING  ORE  AND  REAGENTS. 
CALCINATION  AND  ROASTING. 
REDUCTION  AND  FUSION. 
DISTILLATION  AND  SUBLIMATION. 
SCORIFICATION  AND  CUPELLATION. 
INQUARTATION  AND  PARTING. 
WEIGHING  BEADS  AND  BULLION. 
TABULATING  RESULTS  AND  REPORTING. 


PART     SECOND. 

ASSAY  OF  LEAD. 

"      "  ANTIMONY. 

u      "  GOLD  AND  SILVER. 

"      "  PLATINUM. 

"      "  ZINC. 

"  MERCURY. 

"      "  BISMUTH. 


"      "    COPPER. 

"      "    IRON. 

"      "   NICKEL  AND  COBALT. 


"      u    CARBON. 


PART    THIRD. 

SILVEE  BULLION. 

GOLD  BULLION. 

CHLOEINATION  ASSAY. 

LEAD  —  SCHEME  FOE  WET  ASSAY. 

PLATINUM     "        "        "         " 

ZINC 

BISMUTH        "        "        "         " 

TIN  u        u        u         " 

COPPEE         "        "        "         {< 

IEON  "        u        "         " 

MANGANESE  "        "        "          u 

NICKEL          "        "        "         " 

SULPHUR      "       " 


PART    FOURTH. 

PEECIOUS  STONES. 
SCALE  OF  HAEDNESS. 
METALS — CHAEACTEEISTICS. 
OEES — CHAEACTEEISTICS. 
TJ.  S.  COINS — COMPOSITION  AND  VALUE. 
MEASUEES  OF  WEIGHT  AND  VOLUME. 
SPECIFIC  GEAVITY. 
THEEMOMETEES. 

TABLE  OF  VALUES  FOE  GEAIN  WEIGHTS. 
MULTIPLICATION  AND  CUPELLATION  TABLES 
FOE  GOLD. 

BLANK  REPOETS. 
PEOBLEMS  AND  QUESTIONS. 
REFEEENCES  ON  ASSAYING. 


APPENDIX. 

MANIPULATION,  FORMULAE,  AND  CALCULATION. 
BLOWPIPE  ANALYSIS,  APPARATUS,  AND  EEAGENTS. 
CHEMICAL  APPARATUS  AND  REAGENTS. 
ASSAYER'S  OUTFIT. 
SPECIAL  METHODS  FOR  GOLD  ORES  AND  ALLOYS. 

OUTLINE  EXAMINATION  SCHEME  FOR  THE  ASSAY  OF 
ORES. 

RULES  FOR  THE  EXAMINATION  OF  A  MINE. 
SCHEME  FOR  QUALITATIVE  ANALYSIS— ZETTNOW. 


PART  I. 

INTRODUCTION,  APPARATUS,  REAGENTS  AND 
OPERATIONS. 


/*&       C,,HF        -,      > 

(UNIVERSITY 

\^£^lb~- 


INTRODUCTION. 


Assaying  has  for  its  object  the  determination  and  extrac- 
tion of  the  metallic  elements  from  their  various  compounds. 

The  rules  are  empirical,  and  a  knowledge  of  chemistry  is 
not  absolutely  necessary,  although  the  assay er  will  find  that 
a  familiarity  with  chemical  laws  and  reactions  will  greatly 
facilitate  his  work.  The  following  is  a  list  of  the  elementary 
bodies  with  the  exception  of  one  or  two  recently  discov- 
ered, and  their  atomic  weights  and  symbols.  An  element 
is  a  body  which  chemical  research  has  failed  to  reduce  to 
a  more  simple  form,  or  separate  into  constituent  parts. 
The  symbol  of  an  element  is  generally  the  first  letter  or 
letters  of  its  Latin  name ;  and  its  atomic  weight  is  the 
smallest  amount  of  that  element  which  will  enter  into  com- 
bination with  other  elements ;  the  first  column  of  figures 
being  the  old  and  the  second  the  new  system  of  atomic 
weights.  Hydrogen  is  taken  as  unity  in  both  systems. 


14 


INTRODUCTION. 


TABLE  OF  ATOMIC  WEIGHTS. 

Revised  by  C.  F.  CHANDLER,  Oct.,  1881. 

Aluminium, 

Al.    IV. 

27-0 

Manganese, 

Mn.       VI. 

55-0 

Antimony, 

8b.     V. 

120-0 

Mercury, 

Hg.        II. 

200-0 

Arsenic, 

As.    V. 

74-9 

Molybdenum, 

Mo.       VI. 

96-0 

B  mum, 

Ba.   II. 

136-8 

Nickel, 

Ni.        VI. 

59-0 

Bismuth, 

BL     V. 

210-0 

Nitrogen, 

JV.          V. 

14-0 

Boron, 

B.    III. 

11  -0 

Osmium, 

Os.  II.  IV. 

199-0 

Bromine, 

Br.      I. 

79-7 

Oxygen, 

0.          II. 

16-0 

Cadmium, 

Cd.    II. 

112-0 

Palladium, 

Pd.       IV. 

106-0 

CcBsium, 

Ga.      I. 

133-0 

PJiosphorus, 

P.           V. 

31-0 

Calcium, 

Ca.    II. 

40-0 

Platinum, 

Pb.        IV. 

197-0 

Carbon, 

C.     IV. 

12-0 

Potassium, 

K.           I. 

39-0 

Oerium, 

Ge.  III. 

141-2 

Rhodium, 

Ro.       IV. 

104-0 

Chlorine, 

Gl.      I. 

35-4 

Rubidium, 

Rb.          I. 

85-4 

Chromium, 

Cr.    VI. 

524 

Ruthenium, 

Ru.  II.  IV. 

104-0 

Cobalt, 

Co.   VI. 

59-0 

Selenium, 

Se.         II, 

79.0 

Columbium, 

Gb.    V. 

94-0 

Silicon, 

Si.         IV. 

280 

Copper, 

Cu.    II. 

63-1 

Silver, 

Ag.         I. 

108-0 

Davyum, 

Da. 

154-0 

Sodium, 

Na.         I. 

230 

Didymium, 

D.    III. 

147-0 

Strontium, 

Sr.          II. 

87-5 

Erbium, 

E.   III. 

169-0 

Sulphur, 

S.           II. 

32-0 

Fluorine, 

F.       I. 

19-0 

Tantalum, 

To.         V. 

182-0 

Gallium, 

0a.III. 

69-9 

Tellurium, 

Te.        II. 

128-0 

Grlucinum, 

Gl.     II. 

9-2 

Thallium, 

Tl.           I. 

204-0 

Gold, 

Au.  III. 

196-2 

Thorium, 

Th.       IV. 

231-5 

Hydrogen, 

H.      I. 

1-0 

Tin, 

Sn.        IV. 

118-0 

Indium, 

In.  III. 

113-4 

Titanium, 

Ti.        IV. 

50-0 

Iodine, 

Z        I. 

126-5 

Tungsten, 

W.  IV.  VI. 

184-0 

Iridium, 

Ir.     II. 

198-0 

Uranium, 

IT.         VI. 

240-0 

Iron, 

Fe.  VI. 

56-0 

Vanadium, 

V.          V. 

51-2 

Lanthanum, 

La.  III. 

139-0 

Yttrium, 

Y.        III. 

60-0 

Lead, 

Pb.    11. 

207-0 

Zinc, 

Zn.         II. 

65-0 

Lithium, 

Z£      I. 

7-0 

Zirconium, 

Zr.        IV. 

90-0 

Magnesium, 

Mg.   II. 

24-0 

NOTE.  —  The  Artiads  are  printed  in  Roman,  the  Perissads  in 

italics. 

The  above  table  of  the  atomic  weights  of  the  elements 
was  prepared  for  the  use  of  the  students  of  the  School  of 
Mines,  and  contains  the  latest  values  as  given  by  reliable 
authorities. 


INTRODUCTION.  15 

The  various  methods  for  the  determination  of  the  metals 
in  their  compounds  may  be  classed  under  two  heads : 

1st.   "  Dry  way, ' '  or  assaying  proper. 
2d.   ' '  Wet  way, ' '  or  analysis. 

The  first  includes  all  determinations  by  the  direct  action 
of  heat,  the  various  operations  being  performed  in  furnaces. 

The  second  head  embraces  the  estimation  and  separation 
of  the  elements  by  the  action  of  solvents  aided  or  unaided 
by  heat,  the  use  of  furnaces  not  being  essential. 

There  are  many  cases,  of  course,  where  the  first  class 
merges  into  the  second,  and  vice  versa. 

It  was  originally  intended  to  give  in  the  following  pages 
only  a  few  concise  methods  for  the  estimation  of  the  metals 
in  their  ores  by  fire  assay  ;  but,  as  in  many  ores  the  precious 
metals  are  associated  with  others  which  are  either  of  value 
or  detriment,  and  whose  determination  is  often  necessary,  a 
few  schemes  for  the  treatment  of  such  ores  in  the  wet  way 
have  been  added. 

The  various  operations  which  may  take  place  in  making 
an  assay  proper,  are — 

1st.  Preliminary  testing  of  the  ore. 

2d.  Preparation  of  the  ore,  sampling,  pulverizing,  etc. 

3d.  Weighing  out  the  ore  and  reagents. 

4th.  Calcination  and  roasting. 

5th.  Reduction  and  fusion. 

6th.  Distillation  and  sublimation. 


16  INTRODUCTION. 

7th.  Scorification  and  cupellation. 

8th.  Inquartation  and  parting,  including  solution. 

9th.  Weighing  beads  and  bullion. 

10th.  Tabulating  results  and  reporting. 

All  of  the  above  will  be  described  further  on ;  but  as  some 
of  the  operations  require  great  care  in  their  performance,  a 
few  rules  and  hints  for  the  guidance  of  the  beginner  may 
not  be  out  of  place. 

1st.  Sample  well  and  carefully,  for  without  a  fair  sample 
the  assay  is  useless. 

3d.  Weigh  carefully,  and  adjust  the  balance  before 
and  after  weighing. 

3d.  Always  weigh  an  ore  before  calcining  or  roasting, 
and  always  roast  thoroughly.  If  the  ore  be  wet,  weigh 
both  before  and  after  drying. 

4th.  Never  fill  a  crucible  or  scorifier  more  than  three- 
quarters  full,  and  when  a  crucible  is  removed  from  the  fire, 
tap  it  on  the  floor  to  settle  the  metal,  unless  otherwise  di- 
rected, and  keep  the  same  covered. 

5th.  To  break  a  crucible,  hit  with  a  middle-sized  hammer 
near  the  centre,  so  as  to  break  off  the  top  at  one  blow. 
Then  lay  the  bottom  on  the  anvil,  and  crack  it  through  to 
get  the  button  out  whole.  Never  break  until  perfectly 
cold. 

To  break  a  scorifier,  lay  it  bottom  up  on  the  anvil ;  en- 
circle with  the  hand,  and  then  strike  the  bottom.  The 
button  will  generally  come  out  free  from  slag. 

6th.  Never  take  a  scorification  or  cupellation  from  the 
furnace  to  finish  at  a  future  time,  but  complete  the  operar 


INTKODUCTION.  17 

tion  at  once.   When  buttons  are  to  be  scorified  or  cupelled, 
be  sure  that  they  are  free  from  moisture. 

7th.  Be  certain  that  all  reagents  used  in  an  assay  are  dry 
and  pure,  especially  when  testing  for  the  precious  metals. 

8th.  In  reporting  results,  recollect  that  a  fire  assay  does 
not  always  give  the  exact  amount  of  metal  contained,  but 
often  shows  only  what  the  yield  of  an  ore  would  be  in  smelt- 
ing, and  that  the  assay  of  a  small  piece  of  ore  can  not 
represent  the  value  of  the  bed  or  vein  from  which  it  may 
have  been  taken,  and  word  your  report  accordingly. 

9th.  Always  observe  the  color  and  character  of  the  slag 
produced  in  an  assay,  as  the  nature  of  the  ore  treated  may 
often  be  determined  in  this  way. 

10th.  Never  accept  the  results  of  an  assay  where  the 
fusion  has  been  incomplete,  the  button  formed  being  small 
or  brittle. 


BALANCES  AND  WEIGHTS 

Four  balances  will  be  found  useful  in  an  assay  labora- 
tory. 

a. — A  rough  scales  for  weighing  large  samples  of  ores, 
metals,  fluxes  in  bulk,  &c.  An  ordinary  grocer's  scale  will 
do  for  this  purpose. 

b. — A  balance  for  weighing  out  ore  for  assay,  and  the  but- 
tons of  the  base  metals.  (Fig.  1.)  This  balance  should 


FIG.  1. 

take  ten  ounces  in  each  pan,  turn  with  one-twentieth  of 
a  grain,  and  be  provided  with  movable  pans,  level,  and  set- 
screws  for  adjusting.  It  is  generally  placed  on  a  box,  fur- 
nished with  a  drawer  for  weights. 

c.— Hanging  scales  for  fluxes.  The  pans  should  be  made 
of  horn,  and  supported  by  threads  to  a  brass  beam.  It  should 
carry  at  least  ten  ounces,  and  turn  with  one-half  grain. 


BALANCES  AND  WEIGHTS. 


19 


d.—  The  button  or  bullion  scale.  (Fig.  2.)  This  balance 
should  be  used  for  nothing  but  gold  and  silver  beads,  or 
bullion,  and  must  be  accurate  and  extremely  sensitive. 


FIG.  2. 

When  loaded  with  one  gramme,  it  should  turn  with  one 
one-twentieth  of  a  milligramme,  and  requires  to  be  han- 
dled with  the  greatest  care.  It  is  provided  with  steel  knife- 
edges,  agate  bearings,  spirit  level,  and  set-screws. 

To  ADJUST  THIS  BALANCE.  —  First  turn  the  set-screws,  two 
at  a  time,  until  the  bubble  is  in  the  centre  of  the  level,  and 
the  balance  is  firm.  Then  note  the  number  of  divisions  the 
needle  indicates  on  the  scale  when  vibrated,  counting  from 
the  second  swing.  If  it  shows  equally  on  both  sides  of  the 
centre  line  it  is  correct.  Never  leave  the  rest  down,  or  raise 
it  when  the  needle  is  not  near  the  centre  line,  as  the  knife- 
edges  are  likely  to  be  thrown  off  their  bearings  and  the 
balance  injured.  To  clean,  an  artist'  s  blending-brush  is  very 


convenient,  as  it  is  soft  and 


20  BALANCES  AND  WEIGHTS. 

THE  WEIGHTS  employed  by  the  assayer  are— 

a. — Avoirdupois  for  ores,  base  metals,  and  fluxes. 

&. — Troy  for  gold,  silver,  &c. 

G. — The  French  system  based  upon  the  gramme  as  a  unit. 
These  weights  can  be  used  for  weighing  ores,  fluxes,  and  re- 
sults ;  and  will  always  be  found  convenient,  as  they  are  on 
the  scale  of  ten. 

d. — The  assay  weights,  which  is  a  system  made  up  from 
a  comparison  of  the  three  foregoing,  will  be  found  ex- 
tremely simple  and  useful,  saving  a  vast  amount  of  calcu- 
lation and  labor  (see  table,  page  149). 

The  unit  of  the  system  is  the  assay  ton=29.166  grammes. 
Its  derivation  will  be  seen  at  a  glance. 

One  Ib.  Avoirdupois =7, 000  Troy  grains. 

2,000  Ibs.  =  one  ton. 

2,000  x  7,000=14,000,000  Troy  grains,  in  one  ton  Avoirdu- 
pois. 

480  Troy  grains —\  oz.  Troy. 

14, 000, 000^480^29,166  + Troy  ozs.  in  2,0001bs.  Avoirdu- 
pois. . 

There  are  29,166  milligrammes  in  one  assay  ton  (A.  T.) ; 
hence — 

2,000  Ibs.  is  to  1  A.  T.,  as  1  oz.  Troy  is  to  1  milligramme. 

EXAMPLE. — Weigh  an  A.  T.  of  ore,  and  if  on  assay  it 
yields  1  milligramme  of  gold  or  silver,  the  result  reads  one 
Troy  oz.  in  2,000  Ibs.  Avoirdupois,  without  further  calcula- 
tion. 

Should  the  assayer  desire  to  make  quantitative  determi- 
nations in  the  wet  way,  he  will  require,  besides  the  above, 
an  analytical  balance,  which  will  carry  100  grammes  in  each 
pan,  and  turn  with  one-twentieth  of  a  milligramme.  This 
balance  should  be  provided  with  apparatus  for  taking  spe- 
cific gravities,  rider,  and  weighing-tubes. 


FURNACES  AND  FUELS. 


. 

• 


FURNACES  AND  FUELS. 

1st.  FURNACE  FOR  CALCIN- 
ING OR  ROASTING. —  Fig.   3 
represents  two  sections. 

The  rireplace  is  made  shal- 
low ;  and,  as  a  high  tempera- 
ture is  not  required,  it  may  be 
made  of  red  brick,  or  only 
lined  with  fire-brick,  and  the 
body  of  the  furnace  bound 
with  strap-iron. 

It  should  also  have  a  cast- 
iron  top-plate. 

The  grate-bars  may  be  in 
one  piece  or  separate,  and 
draw  out.  The  ash-pit  should 
be  provided  with  a  door, 
which  may  be  closed  or  opened 
in  order  to  regulate  the  draft. 

A  hood  of  sheet-iron  will 

FIG.    3. 

scale  i^-inch  to  the  foot.  also  be   f  ound   necessary  in 

many  cases,  as  the  fumes  given  off  in  roasting  are  often  in- 
jurious. It  is  an  excellent  plan  to  have  the  hood  of  gal- 
vanized iron  to  prevent  rusting. 

The  chimney  may  be  of  brick,  iron  or  clay. 

2d.  FURNACES  FOR  FUSION  OR  MELTING  (Figs.  4  and 
4a). — These  furnaces  should  be  deeper  than  the  preceding 
one,  and  like  it,  may  be  built  of  red  brick,  but  it  is  better 
to  line  them  with  fire  brick. 

For  heavy  work  the  furnaces  should  be  low,  to  facilitate 
the  lifting  in  and  out  of  crucibles.  Sometimes  a  crane  is 
added  for  this  purpose. 


FUENACES   AND   FUELS. 

The  chimney  ought  to  be  of  brick, 
and  the  larger  and  higher  it  is,  the 
stronger  the  draft.  This  may  be 
regulated  by  a  damper  as  well  as 
by  the  ash-pit  door. 

c  The  tops  should 

be  of  cast-iron, 
and  the  cover  lift 
or  slide  easily. 
An  iron  shelf 
can  be  placed  in 
front  to  hold  in- 
got moulds  when 
metals  are  to  be 
poured,  as  shown 
in  Fig.  4a,  which 
shows  in  section 
the  furnace  used 


FlG.  4. — Scale  ^-inch  to  the  foot. 

for  deposit  melting  in  the  United  States 
mints. 
3d.  MUFFLE  FURNACES  FOE  SCOEIFICA- 

TION      AND      CUPELLA- 

TION.      Fig.    5    shows 
'  sections    of    a    porta- 
ble cupel 
furnace. 


FIG.  5. 
Scale  %-inch  to  the  foot. 


FlG.  40.  —Scale 


FURNACES   AND   FUELS. 


The  same  furnace  may  be  used  for  both  operations,  but 
generally  it  will  be   found  convenient  to  have    a  larger 

muffle  for  scorifi- 
cation  and  higher 
heat. 

The  muffles  are 
made  of  refrac- 
tory clay,  and  in 
one  piece ;  and 
should  be  thor- 
oughly dried  be- 
fore using. 

The  draft  of  the 
furnace  ought  to 
b  e  sufficient  t  o 
carry  off  lead 
fumes,  which  are 
injurious.  The 
construction  o  f 
the  furnace  will 
vary  with  the  fuel 
used  and  work  to 
be  done. 

Fig.  6  shows  the 
vertical  and  hori- 
zontal sections  of 
a  double  muffle 
scorification  fur- 
nace, for  works 
where  a  large  number  of  scorifications  are  required. 

It  has  been  in  use  in  the  assay  laboratory  of  the  School 
of  Mines,  New  York,  for  two  years,  and  its  value  has  been 


_£ 


FIG. 

Scale  %-inch  to  the  foot. 


24  FUKNACES   AND   FUELS. 

proved.     The  muffles  are  larger  than  usual,  and  can  be 
drawn  out. 

The  whole  furnace  is  lined  with  fire  brick,  as  is  indicated 
by  the  fine  shading. 

By  placing  a  damper  at  the  top,  one-half  may  be  used 
to  the  exclusion  of  the  other. 

Fig.  6a  is  an  assay  furnace  for  the  use  of  soft  coal.  This 
furnace  has  the  following  advantages :  1st.  Economy  of  fuel. 
A  furnace  containing  8xl4-inch  muffles  may  be  run  for 
eight  hours  with  not  more  than  100  Ibs.  of  coal.  Any  free- 
burning  coal  may  be  used  (the  Canon  City  coal  of  Colorado 
—a  lignite — gives  very  excellent  results).  2d.  Economy  of 
construction.  Yery  few  fire  brick  and  other  material  are 
required,  and  the  furnace  may  be  built,  exclusive  of  stack, 
for  from  $25  to  $50.  3d.  Saving  in  muffles.  The  muffle  not 
being  in  contact  with  the  fuel,  and  subjected  only  to  the 
action  of  the  flame  and  gases,  does  not  become  covered 
with  slag,  but  always  remains  clean  and  is  easily  heated. 
When  two  muffles  are  employed,  the  upper  one  is  suffi- 
ciently hot  for  cupellation,  but  not  for  scorification.  The 
coal  should  be  broken  to  the  size  of  the  fist,  or  smaller. 
The  muffles  are  sufficiently  hot  for  charging  in  from  thirty 
to  sixty  minutes  after  the  fire  is  lighted.  The  heat  is 
easily  regulated  by  means  of  the  damper  closing  the  ash 
pit. 

THE  FUELS  employed  are  coke,  anthracite,  bituminous 
coal,  and  charcoal.  Sometimes  oil  and  gas  are  used  for 
small  laboratory  furnaces. 

The  coke  should  be  about  egg  size  and  free  from  sul- 
phur. It  is  chiefly  used  in  calcining  and  fusion  fur- 
naces. 

Charcoal,  coke,   anthracite,  and  bituminous  coal  may 


Section  through  L.  M. 


Section  through  E.  F*  Section  "through  G.  K 


FIG.  Qa. 
ASSAY  FURNACE  FOR  BURNING  SOFT  COAL. 

Muffles  8x15  inches. 
Bind  with  lx|  inch  iron. 

Ash  pit  and  coaling  hole  closed  by  sheet  iron  door,  the  latter  resting  on  the 
binders. 


26  CKUCIBLES. 

be   employed  for  the  muffle  furnace.      Bituminous  coal 
should    have,    however,   a    special    furnace.       (See    Fig. 

Anthracite  coal,  stove  size,  is  best  adapted  for  the  assay- 
er's  purpose,  but  charcoal  may  be  used  as  a  substitute  for 
either  coke  or  anthracite,  when  it  can  be  had  more  cheaply  ; 
it  gives  a  hot  fire,  and  is  easily  regulated  ;  but  requires 
constant  attention,  and  the  pieces  used  should  be  of  me- 
dium size. 

Oil  and  gas  furnaces  are  used  with  varying  results,  but 
the  limits  of  this  work  will  not  permit  a  description  of 
them.  See  "Mitchell's  Manual  of  Practical  Assaying," 
pages  71  to  107  inclusive.  Also  circular  of  the  Buffalo 
Dental  Manufacturing  Company. 

In  lighting  a  fire  it  will  be  found  convenient  to  use 
pieces  of  cork  or  corncobs  saturated  with  rosin,  which 
burn  well,  are  cheap,  and  save  much  trouble,  as  they  give 
no  dirt. 

To  use,  it  is  only  necessary  to  light  a  piece  and  lay  it 
upon  a  little  kindling-wood  placed  in  the  bottom  of  the  fur- 
nace, then  put  a  few  pieces  of  wood  on  top  and  add  the 
coal  after  the  wood  has  kindled. 


CKUCIBLES. 

A  good  crucible  should  stand  sudden  changes  of  tempera- 
ture, be  infusible,  impermeable,  and  not  attacked  by  fused 
substances. 

The  crucibles  in  use  may  be  arranged  in  the  following 
order. 

1.  Black  lead  or  graphite  for  fusing  metals. 


CRUCIBLES. 


2.   French  clay. 
(Fig.  7.) 


3.  Hessian 
sand  crucibles, 
round  and  tri- 
angnlar.  (Fig. 

8.) 


FIG.  8. 


FIG  7. 

4.  Charcoal-lined  crucibles. 

The  most  refractory  crucibles  are  cut  out  of  quick  lime, 
or  can  be  moulded  from  magnesia,  and  chloride  of  magne- 
sium, but  the  latter,  however,  are  soft  and  not  very  strong. 

The  composition  of  the  black  lead  crucibles  is  generally 
one  to  seven  parts  of  refractory  clay,  and  three  to  ten  of 
graphite  ;  but  sand  is  sometimes  used.  If  the  crucibles 
contain  too  much  silicious  matter  they  are  liable  to  be 
acted  upon  by  the  melted  charge,  or  the  bases  contained 
in  the  coal  around  them,  when  in  the  fire. 

These  crucibles  run  in  sizes  from  1  to  400.  The  smallest 
holding  from  two  to  three  ounces  of  metal.  The  next,  four 
to  six,  and  so  on. 

The  demand  is  for  two  kinds,  " steel"  and  "brass;" 
but  they  can  be  employed  for  melting  all  substances  which 
are  not  oxidizing  in  their  action. 

French  crucibles  are  made  of  Paris  clay  and  fine  sand, 
and  rank  among  the  best,  but  are  more  expensive  than  the 
Hessian.  For  melting  charges  which  can  be  poured,  they  are 
superior  as  the  crucible  can  be  used  again.  The  sizes  run 
from  1  to  20,  with  covers  to  match. 

The  composition  of  the  ordinary  Hessian  crucible  is  about 
chree-quarters  clay  (German),  and  one -quarter  sand.  They 


28  CRUCIBLES. 

are  round  and  triangular,  and  run  in  regular  sizes,  viz: 
Small  fives,  large  do.,  up  to  eights.  Halves,  holding  one- 
half  gallon,  and  ones,  holding  one  gallon,  with  covers  to 
match. 

The  charcoal  crucible  is  made  by  lining  an  ordinary  clay 
or  Hessian  crucible  with  a  mixture  of  charcoal  and  molasses. 
The  charcoal  employed  should  be  very  fine,  and  only  just 
enough  molasses  used  to  hold  it  together.  The  mixture 
is  then  packed  into  the  crucible  as  tightly  as  possible,  dried 
slowly,  and  bored  out  to  any  extent  desirable. 

Sometimes  water  and  gum  are  substituted  for  molasses. 

Fig.  9  represents  three  kinds 
of  charcoal  lined  crucibles. 


Alumina  crucibles  for  some 
operations  are   very  satisfac- 
.  9.  tory  when  intense  heat  is  re- 

quired, but  lime  will  answer  as  well. 

The  choice  of  a  crucible  depends  upon  the  nature  of  the 
substance  to  be  treated  in  it,  the  temperature  of  the  fire, 
and  the  time  it  is  to  remain  exposed  to  the  action  of  heat. 

If  a  charge  be  basic  the  crucible  should  be  basic  also,  and 
vice  versa.  The  grain  and  appearance  of  the  crucible  should 
be  taken  into  consideration.  Much  iron  will  render  the 
crucible  fusible. 

To  test  a  crucible  for  fusibility,  heat  a  piece  of  the  cru 
cible  and  see  if  the  corners  are  rounded,  or  if  it  is  fused  on 
the  edges. 

For  corrosive  action  fuse  litharge  in  the  crucible.  For 
permeability  fill  two  crucibles  with  water  and  note  the  time 
required  for  it  to  run  out,  the  one  which  holds  the  best  be- 
ing preferable.  As  a  rule,  crucibles  resist  permeation  and 
corrosion  in  the  proportion  of  the  fine/less  and  regularity 


CUPELS. 


of  grain,  but  their  tendency  to  crack  is  increased  in  the 
same  ratio. 

The  action  of  sudden  changes  of  temperature  may  be  as- 
certained by  heating  suddenly,  and  cooling  first  in  air  and 
afterwards  by  plunging  in  cold  water. 
ROASTING  DISHES,  (Fig.  10),  and  SCOKIFIERS,  (Fig.  11.) 

Both  dishes  and  scori- 
fiers   are  made  of  re- 
FIG.  11.   fractory  clay  the  same 
FIG.  10.  as    crucibles.      They 

should  resist  the  action  of  litharge  and  not  be  too  deep. 
Painting  with  water  and  oxide  of  iron  prevents,  to  some 
extent,  the  cutting  by  strong  bases. 

Scorifiers  may  be  bought  or  made,  but  as  a  rule  it  is 
better  to  buy  them,  as  they  will  stand  transportation  and  it 

requires  some  care  to 
make  good  ones. 

A  section  of  a  good 
scorifier  is  uniform  in 
character.  It  is  close, 
and  should  show  no 
flaws  or  cracks.  (Fig. 
lla.) 


FIG.  lla. 


CUPELS. 


These  vessels  are  generally  made  of  the  ashes  of  burnt 
bones,  freed  from  organic  matter,  ground  and  washed. 
Horses'  or  sheep  bones  are  said  to  be  the  best. 

It  is  better  to  make  cupels  than  to  buy  them,  especially 
when  they  have  to  be  carried  some  distance.  The  prepared 
bone-ash  can  be  obtained  in  bulk,  and  is  mixed  with  just 
sufficient  warm  water  to  cause  it  to  hold  together  without 


30 


CUPELS. 


being  moist.  Sometimes  in  mixing  the  bone-ash  a  little 
wood  ashes  is  added,  or  a  spoonful  of  "pearl-ash,"  (car- 
bonate of  potash),  by  dissolving  it  in  the  water  used  for 
moistening  the  bone-ash. 

Too  much  bone-ash  should  not  be  mixed  at  once,  as  it 
dries  quickly. 

If  the  bone-ash  is  too  fine  or  too  coarse  it  works  badly  ; 
as  in  the  first  case  the  cupel  will  crack  upon  drying,  and  in 
the  second,  be  too  porous,  absorb  silver  with  the  litharge 
and  occasion  loss. 

The  cupel  is  formed  by  filling  and  driving  the  prepared 
bone-ash  into  a  mould  made  for  the  purpose. 

The  right  degree  of  compression  should  be  used,  as  other- 
wise the  cupel  will  be  either  too  hard  or  too  porous.  A 
little  experience  will  tell  the  operator  when  he  has  reached 
^J|  the  proper  point.  When  completed  it  presents  the 
FIG.  12.  appearance  of  Fig.  12. 

Care  should  be  used  in  drying,  plenty  of  time  being 


-Y 


PLAN  OF  PORTION  -A* 


SECTION  ON  LINE  X.  Y. 

FIG.  I2a. — ENGLISH  SQUARE  CUPEL. 


LUTES.  31 

allowed,  and  all  moisture  and  organic  matter  expelled  pre- 
vious to  using,  by  heating  in  a  furnace.  Sometimes  a  cupel 
is  made  of  coarse  bone-ash,  and  the  surface  finished  off  with 
fine  washed  material. 

Cupels  dried  in  the  sun  are  better  than  those  dried  arti- 
ficially. They  are  not  so  liable  to  crack. 

In  the  Royal  Mint,  London,  England,  an  improved  form 
of  cupel  is  in  use.  It  is  square,  with  four  depressions  for 
holding  the  same  number  of  buttons,  enabling  the  operator 
to  run  two  assays  in  duplicate  in  the  same  cupel.  Fig.  I2a 
represents  the  method  of  making,  and  the  cupel  when  fin- 
ished. Iron-bound  cupels  are  sometimes  used  when  the 
amount  to  be  cupelled  is  large,  especially  in  treating 
sweeps. 

LUTES,  CEMENTS  AND  WASHES. 
GOOD  FIEE  LUTES. 

1.  Fire  clay,  two  parts. 
Sharp  sand,  eight  parts. 
Horse  dung,  one  part. 

Mix  well  and  temper  the  same  as  mortar,  until  fche  de- 
sired consistency  is  reached. 

2.  Fire  clay,  one  part. 
Sand,  three  parts. 

Mix  with  a  little  hair  and  weak  borax  water. 

3.  Zinc  cement. 

Dissolve  three  per  cent,  of  borax  in  water  to  about  1.49 
specific  gravity  and  then  add  calcined  oxide  of  zinc  to  suit. 

OTHER  LUTES. 

Plaster  of  paris  mixed  with  water,  milk,  glue,  or  starch 
water  makes  a  good  lute,  and  will  stand  a  red  heat.  Wax 
or  paraffin  is  useful  for  bottles,  stoppers,  etc.,  also  tallow 


32  TOOLS. 

or  stearic  acid.  Faraday's  cap  cement  is  made  by  melting 
together  rosin  five  parts,  yellow  beeswax  one  part,  and  stir- 
ring in  one  part  of  red  ochre. 

A  fine  lute  for  iron  vessels  is  porcelain  clay  (kaolin) 
mixed  with  a  solution  of  borax  in  water. 

A  good  lute  for  glass  vessels,  is  quicklime  slaked  in 
the  air  and  then  beaten  into  a  liquid  paste  with  white  of 

egg. 

Where  corrosive  vapors  are  liable  to  escape,  a  lute  made 
of  fire  clay  and  boiled  linseed  oil  should  be  applied,  and 
covered  with  slips  of  linen  spread  with  the  lute  of  lime  and 


To  LINE  CRUCIBLES. 

Fine  sifted  charcoal  mixed  with  gum  water,  borax  water, 
or  molasses  enough  to  hold  when  pressed  together  in  the 
hand,  without  being  wet  or  sticky.  It  should  contain  no 
lumps. 

WASH  FOR  CRUCIBLES  AND  SCORIFIERS. 

1st.  Finely  pulverized  chalk  and  water. 

2d.  Sesquioxide  of  iron  (hematite)  and  water. 


TOOLS. 

The  tools  required  by  the  assayer  are  regulated  more  or 
less  by  the  work  to  be  done. 
The  following  are  the  principal : 
Crucible  tongs  (Fig.  13.)    They  should  be  made  with  long 


FIG.  13. 
handles  for  taking  crucibles  out  of  the  fire,  etc. 


TOOLS.  33 

Scorification  tongs.     (Fig.  14.)    The  spring  should  not  be 


FIG.  14. 

too  strong,  and  the    horse    shoe  part  should  just  fit  the 
scorifier. 
Cupel  tongs.     (Fig.  15.)    These  should  be  made  of  steel 


FIG.  15. 
and  about  two  and  one-half  feet  long  with  an  easy  spring. 

Three  hammers  are  useful.  One  large  for  hammering 
metal,  one  medium  for  breaking  crucibles  and  scorifiers,  and 
one  small  for  marking  lead  buttons. 

A  set  of  small  steel  dies  from  0  to  9  inclusive,  and  large 
and  small  alphabet  for  marking  buttons  and  bullion  will  be 
found  useful,  but  are  not  necessary. 

Three  pokers  are  convenient,  small,  large,  and  medium. 

One  or  two  small  hoes  or  scrapers  for  cleaning  out  the 
bottom  of  the  cupel  muffle.  (Fig.  16.) 

/ ^  tg 

FIG.   16. 

A  pair  of  cutting  shears  and  nippers  for  cutting  wire  for 
lead  assay,  etc. 

A  small  vise  and  anvil,  medium  size,  with  a  suitable 
bench  for  the  same. 

Wooden  mallets,  light  and  heavy,  for  packing  crucibles, 
making  cupels,  etc. 

Files  and  cold  chisels  for  sampling  and  cutting  metals. 
Charcoal  saw  for  blow-pipe  charcoal,  and  crucible  tops. 

Two  iron  mortars  and  pestles,  and  if  much  ore  is  to  be 
pulverized,  a  grinding  plate  and  rubber,  as  shown  in  Fig. 


/^          O.THP 

nOTNIVERsiTY 
^^   c 


34 


TOOLS. 


17,    will  be  a  great  convenience  and  save  labor.     The  plate 

is  a  flat  iron  casting 
18x24  inches,  and  1 
inch  thick.  The  sur- 
face used  being  planed 
smooth.  The  rubber 
or  grinder  is  a  piece  of 
cast  iron,  4x6  inches 
FIG.  17.  square,  1J  inches  in 

the  middle,  by  |  of  an  inch  thick  at  the  ends ;  thus 
giving  a  slightly  convex  surface,  which  should  be  true 
on  the  board  at  all  points.  To  conduct  the  operation 
place  the  left  hand  upon  the  rubber,  throwing  the  weight 
of  the  body  upon  it,  and  then  grasping  the  handle 
with  the  right  hand,  move  the  iron  rubber  back  and  forth, 
depressing  the  handle  when  pushing  forward  and  raising  it 
in  drawing  back.  For  laboratories  where  large  quanti- 
ties of  ore  are  to  be  pulverized,  the  size  of  the  plate,  and 
the  weight  of  the  rubber  should  be  increased  ;  but  for 
ordinary  use  the  dimensions  given  will  be  found  suffi- 
cient. 

The  operation  is  much  more  rapid  than  in  the  ordinary 
mortar  and  pestle  style,  and  the  manipulator  after  a  little 
practice  has  complete  control  over  the  ore  treated. 

Should  it  not  be  convenient  to  use  the  plate  and  rubber, 
a  long  handled  pestle  coming  up  to  the  chest  will  be  found 
an  improvement,  as  the  mortar  can  be  placed  on  the  floor 
and  the  pestle  worked  while  the  operator  is  in  a  standing 
position. 

A  series  of  sieves,  from  twenty  to  one  hundred  mesh,  will 
be  useful  for  sifting  ores  and  fluxes.  The  box  sieve,  (Fig. 
18),  is  a  simple  arrangement,  and  consists  of  a  round  tin 


TOOLS. 


35 


FIG.  18. 


box  with  a  sieve  fitting  into  it  as 
represented  in  the  engraving.  The 
sieve  is  a  tin  frame  with  any  desired 
mesh  gauze  soldered  to  it,  and  fits 
tightly  in  the  box.  The  advantage  gained  by  its  use 
is  that  in  sifting  the  pulverized  ore  there  is  no  dust.  The 
fine  material  being  passed  through  the  sieve  is  kept  from 
flying  around.  The  size  most  convenient  is  8  inches  in  di- 
ameter, the  box  2  inches  deep,  and  the  rim  of  the  sieve  2 
inches,  fitting  about  £  inch  into  the  box.  A  tin  cover  can 
be  placed  over  the  whole. 

Open  and  closed  ingot  moulds  for  casting  lead  and  silver 
bars,  ingots,  etc. 

Hand  button-rolls  for  gold  and  silver  only. 
They  should  be  kept  covered  and  free  from 
dust. 

Cupel  mould,  (Fig.    19.)      This   consists  of 
two  parts,   an  iron  ring  and  a  steel  pestle  or 
FIG  19         driver,  just  fitting  into  the  ring. 
A  mould  for  pouring  the  assay  charge  in  scorification. 

9  (Fig.  20. )   This  should  be  of  heavy  sheet 

iron  or  copper.  It  saves  much  time,  and 
by  employing  it,  the  scorifiers  can  be 
used  again.  Larger  moulds  of  the  same 
style  will  be  found  convenient  for  pour- 
ing crucible  charges,  but  are  not  neces- 
sary, unless  crucibles  are  scarce. 

Shovels  for  coke  and  coal,  and  a  small 
hatchet  for  splitting  kindling  wood. 
The  coke  shovel  should  be  ribbed  or 
perforated  so  that  the  fine  coke  or  dust 
may  fall  through. 


ooo 
ooo 
ooo 


,  20. 


TOOLS. 


Mixing  scoops  of  Russia  sheet  iron  3J  by  five  inches, 
with  straight  sides  and  back  about  |  inch  high.  They  are 
convenient  for  mixing  lead  or  silver  crucible  charges  in,  and 
owing  to-  the  high  finish  of  the  iron,  the  assay  on  being 
poured  out  does  not  cling  to  the  scoop,  a  few  sharp  taps 
detaching  everything. 

A  tin  sampler,  shown  in  Fig.  21.  will  be 
found  very  useful.  It  consists  of  a  series 
FIG  21.  °f  troughs  arranged  in  a  row  and  fastened 
together  at  equal  distances  by  a  tin  strip  soldered  on  their 
ends.  A  shovel  full  of  ore  emptied  by  a  series  of  shakes 
upon  them,  is  just  half  caught  by  the  troughs  ;  one-half 
going  through  the  openings  between.  By  repeating  this 
operation,  the  size  of  the  sample  can  be  reduced  to  any  ex- 
tent desired. 

A  laboratory  desk,  as  shown  in  Figs.  22  and  23,  will  be 


o 


FIG.  22.   Section. 
Scale  }&  inch  to  the  foot. 


FIG.  23.  Elevation. 
Scale  ^3  inch  to  the  foot. 


APPARATUS.  37 

found  a  very  suitable  and  compact  arrangement.  It  con- 
sists of  four  parts,  shelves  for  bottles,  closet  for  ore- 
scales,  drawer  for  cupels  and  apparatus,  and  double  closet 
for  crucibles,  scorifiers,  etc.  The  illustrations  being  made  to 
a  scale,  the  desk  can  be  constructed  from  them  without 
trouble. 

This  style  of  desk  has  been  in  use  in  the  School  of 
Mines,  New  York,  for  some  years,  and  has  been  found 
most  convenient.  The  lower  closet  should  be  provided  with 
a  shelf  and  the  drawer  with  partitions.  If  gas  can  be  had, 
each  desk  in  a  laboratory  should  have  a  burner  above  for 
lighting  purposes,  and  two  or  three  large  jets  to  which  rub- 
ber tubes  can  be  fastened  so  that  Bunsen  burners  can  be 
employed  on  the  desk.  These  jets  are  best  placed  next  the 
scale  closet. 


APPARATUS. 

The  amount  and  kind  of  apparatus  required  by  the 
assayer  varies,  but  the  following  list  will  be  found  about  all 
that  will  be  needed  for  ordinary  work  : 

About  three  dozen  quart  bottles  for  reagents,  glass  stop- 
pered. One  dozen  glass-stoppered  parting  bottles,  for  bul- 
lion assay.  Eight  oz.  is  a  good  size.  The  stoppers  should 
be  square-topped  and  fit  exactly,  so  that  the  bottles  will 
not  leak  when  shaken. 

An  assortment  of  corked  bottles  of  different  sizes  for 
samples. 

Two  or  three  ring  stands  and  the  same  number  of  Bunsen 
burners  or  alcohol  lamps.  The  former  are  preferable,  if 
gas  can  be  had,  and  should  be  provided  with  two  or  three 
feet  of  rubber  tubing  for  each  burner. 


88  APPARATUS. 

Two  wash  bottles,  one  small  and  one  large,  say  one-half 
pint  and  quart. 

One  half-dozen  horn  spatulas  or  spoons  for  mixing  ore. 
Some  iron  pans  for  roasting.  The  ordinary  long  handled 
frying  pan  is  suitable,  and  should  be  about  the  size  of  the 
furnace  top.  Before  roasting  it  should  be  lined  with  chalk 
or  oxide  of  iron.  One  dozen  parting  flasks,  (Fig.  24,) 
for  gold  bullion  assay ;  also  annealing 
cups  for  the  same  purpose.  These  are  of 
clay  and  made  thin.  (Fig.  25.) 

Brushes   for  ores   and  fluxes  made  of 
FIG  25  camel' s  narr  5    a  large  feather  trimmed, 
makes  an  excellent  substitute. 

A  few  dozen  sheets  of  glazed  paper,  or  stout  manilla 
paper  when  glazed  paper  cannot  be  had,  for  mixing  ore 
upon.  Black  is  preferable,  and  when  held  up  to  the  light, 
there  should  be  no  holes. 

Hessian  and  French  crucibles  and  covers  of  various  sizes 
and  shapes. 

Scorifiers,  large  and  small. 

Scorification  and  cupel  muffles  to  suit  furnaces. 

Cupels  from  f  to  1J  inches  in  diameter. 

These  should  always  weigh  more  than  the  button  to  be 
cupelled. 

Glass  beakers  and  rods.  Funnels  for  filtering.  Gum 
labels,  note  book,  towels,  large  and  small  porcelain  mortars, 
balances,  scales  and  weights,  as  have  been  described. 

For  volumetric  work,  silver  bullion,  etc.,  graduated 
flasks,  pipettes  and  burettes,  will  also  be  necessary.  See 
bullion  assay,  page  112. 

Should  the  assayer  wish  to  be  prepared  for  all  kinds  of 
work,  it  would  be  well  for  him  to  provide  himself  with  the 


BEAGENTS   AND   CHEMICALS.  39 

complete  list  of  tools  and  apparatus,  given  on  pages  188 
and  191,  Appendix,  or  at  least  in  addition  to  the  articles 
which  have  been  described,  with  iron,  clay  and  glass  re- 
torts, agate  mortar  (large),  one  or  two  platinum  crucibles 
and  dishes,  and  a  couple  of  Bunsen  battery  cells.  The 
prices  of  the  various  articles  are  given  in  the  list,  so  that 
an  estimate  can  be  made  of  the  probable  cost  of  starting 
an  assay  laboratory. 

REAGENTS  AKD  CHEMICALS. 

These  may  be  divided  into  seven  classes. 

a.  Reducing.     To  this  class  belong  those  bodies  which 
have  the  power  of  removing  oxygen  from  its  combinations. 

b.  Oxidizing.     All  bodies   which  give   up  oxygen  with 
facility. 

c.  Desulphurizing.     This   class  includes  all    substances 
which  possess  a  strong  affinity  for  sulphur,  and  will  decom- 
pose its  compounds  under  the  action  of  heat  or  in  solution. 

d.  Sulphurizing.     Sulphur  and  such  of  its  compounds  as 
give  up  their  sulphur  easily  upon  elevation  of  temperature 
or  in  solution. 

e.  Fluxes.  Under  this  head,  we  include  a  large  class  of 
bodies,  but  generally  they  are  substances  which  render 
others  to  which  they  are  added  more  fusible  ;  either  by 
acting  as  a  solvent  or  as  a  decomposing  agent.     Fluxes  are 
either  acid,  basic,  or  neutral  in  their  action. 

f.  Solvents  include  solutions  which  are  used  in  the  wet 
way  only.     Such  as   distilled  water,  nitric,  sulphuric  and 
hydrochloric  acids,  etc. 

g.  Precipitants  in  the  wet  way.     As  the  salt  solution 
used  in  the  bullion  assay. 

The  following  are  the  principal  reagents  and  chemicals 


40  REAGENTS   AND   CHEMICALS. 

employed  by  the  assayer  in  his  work.  There  are,  however, 
many  others  which  might  be  used,  but  they  can  all  be 
classed  under  the  heads  just  given. 

Dry  BICARBONATE  or  SODA  (sodic  bicarbonate,  JNa  HC03) 
or  the  corresponding  potash  salt.  These  act  as  desulphur- 
izing agents,  and  in  some  cases  as  oxidizing  agents.  The 
latter  action  is  due  to  the  carbonic  acid  contained.  Some- 
times they  act  as  basic  fluxes. 

They  should  be  free  from  moisture  and  lumps.  On 
account  of  their  easy  fusibility  they  can  retain  in  suspen- 
sion, without  losing  their  fluidity,  a  large  proportion  of 
finely  powdered  infusible  substances. 

LITHARGE  (PbO),  is  a  basic  flux,  oxidizing  arid  desul- 
phurizing agent,  and  supplies  the  lead  in  the  gold  and 
silver  crucible  assay .  It  should  be  dry,  and  free  from  red 
oxide  of  lead,  as  the  latter  has  the  power  of  oxidizing 
silver,  and  thus  causing  loss  of  that  metal  during  the  assay. 
To  free  litharge  from  the  red  oxide,  fuse  the  same  in  a 
crucible,  and  pour  the  mass  into  a  cold  ingot-mould,  keep- 
ing it  from  the  air  while  cooling.  All  litharge  before  using 
should  be  well  sampled,  and  assayed  for  silver.  To  do  this, 
charge  in  a  crucible- 
Litharge 4  A.T. 

Soda 2     " 

Charcoal 0.7  gm. 

and  cover  with  a  layer  of  dried  salt,  one-quarter  of  an 
inch  thick.  Fuse  in  a  hot  fire  until  completely  liquid,  then 
withdraw,  and  proceed  as  in  the  assay  of  a  silver  ore  (p.  71). 
White  lead  (carbonate  of  lead — plumbic  carbonate,  PbCO3), 
is  sometimes  employed  instead  of  litharge  ;  also,  acetate  of 
lead  for  delicate  experiments. 

BORAX,  CRYSTALLIZED  (2NaBO2.B2O3-10H20).—  This  acts 


KEAGENTS  AND   CHEBl.         H  S I T  Y  )    41 

\^JpsN.A.     y 

as  an  acid  flux ;  but,  on  account  of  the  water  contained, 

it  is  generally  employed  in  a  vitrified  condition,  or  boras; 
glass  (2NaBO2.B9O,),  which  has  a  more  intensified  effect. 
It  has  neither  an  oxidizing  or  desulphurizing  action.  It  is 
sometimes  used  as  a  cover  in  place  of  salt. 

To  prepare — Fuse  the  commercial  borax  in  a  chalk^ 
lined  crucible,  pouring  the  fused  mass  out  on  a  clean  sur- 
face to  cool.  Pulverize,  and  keep  in  a  glass-stoppered 
bottle.  As  borax,  when  heated,  loses  its  water  of  crystal- 
lization, and  undergoes  an  immense  increase  in  volume, 
only  a  little  should  be  added  at  a  time  in  fusing.  Boracic 
acid  (H3B03)  is  also  sometimes  employed. 

SILICA  (Si03),  acts  as  a  good  acid  flux,  and  can  often  be 
used  with  advantage.  A  good  substitute  is  glass  (]STa2Si3 
07+CaSi307+Si02),  as  it  is  easily  fusible,  and  forms  a  good 
slag.  It  should  be  powdered  and  free  from  moisture.  Lime 
glass  is  the  best. 

BLACK  FLUX,  SUBSTITUTE. — A  mixture  of  three  parts 
flour  and  ten  parts  of  bi-carbonate  of  soda  acts  as  a  flux  and 
reducing  agent,  and  is  especially  useful  in  the  lead  assay. 
Black  Flux,  proper =1  of  nitre  and  3  of  argol — deflagrated. 

CYANIDE  or  POTASSIUM  (potassic  cyanide,  KCy=KCN), 
as  a  flux  for  reducing  and  desulphurizing  is  invaluable. 
It  should  be  prepared  with  care  and  kept  in  a  tight  bot- 
tle, as  it  absorbs  moisture.  Take  the  ordinary  commer- 
cial article  and  pulverize  in  an  iron  mortar  as  fine  as  possi- 
ble. Never  sift,  as  the  dust  is  poisonous.  To  protect  your- 
self, cover  the  mortar  with  a  towel,  or  a  board  having  a 
hole  in  the  centre  for  the  pestle. 

FERKO -CYANIDE  or  POTASSIUM  (yellow  prussiate  of  pot- 
ash) (potassic  ferrocyanide,  K4FeCy6+H2O),  will  often 
be  found  useful  as  a  flux  for  reducing  and  desulphum- 


42  REAGENTS   AND    CHEMICALS. 

ing.  The  crystallized  material  should  be  powdered  in  a 
porcelain  mortar,  and  dried  over  a  slow  fire  until  it  is  almost 
white.  If  the  heat  is  too  high  it  will  carbonize  and  turn 
brown. 

AEGOL  (KHC4H4O6),  crude  bitartrate  of  potash,  acts  as  a 
basic  flux  and  reducing  agent.  It  should  be  pulverized 
and  dry,  and  its  reducing  power  determined.  For  this 
purpose  we  charge 

Argol 2  gms 

Litharge 1  A.T. 

Soda i    " 

in  a  crucible,  fuse  in  a  hot  fire,  cool,  extract  the  button  and 
weigh  in  grammes.  Dividing  by  two  gives  the  amount  of 
lead  one  gramme  of  argol  will  reduce  from  litharge. 

CHAECOAL,  acts  as  a  reducing  agent  and  desulphurizer.  It- 
should  be  finely  powdered  and  its  reducing  power  deter- 
mined, as  in  the  case  of  argol.  Using  charcoal  one  gramme, 
and  litharge,  2  A.  T.  Ordinary  wood  charcoal  will  reduce 
twenty-eight  grammes  of  lead  from  litharge. 

STAECH,  flour,  sugar,  and  gum,  may  also  be  used  for  re- 
ducing agents,  but  are  not  so  convenient. 

Dried  starch  reduces  thirteen  parts  of  lead.  Common 
starch  about  eleven  and  one-half  parts.  Sugar  fourteen 
and  one-half,  and  gum  arabic  eleven  parts.  For  some  pur- 
poses pure  hydrogen  gas  will  be  found  essential  as  in  the 
assay  of  oxide  of  tin.  It  is  the  strongest  and  best  reduc- 
ing agent,  but  requires  care  in  its  preparation.  It  is  made 
by  dissolving  zinc  in  dilute  sulphuric  acid,  and  passing  the 
gas  evolved  through  oil  of  vitrol,  to  dry  it  before  using. 
One  part  of  hydrogen  will  reduce  about  one  hundred  and 
four  parts  of  lead  from  litharge. 

METALLIC  IEON  (Fe),  is  a  desulphurizing  agent,  and  is  in 


KEAOENTS  AND   CHEMICALS.  43 

dispensable,  especially  in  the  assay  of  lead  ores.  The 
best  form  is  iron  wire  about  £  inch  in  diameter.  Nails  and 
filings  may  also  be  used. 

PUEE  LEAD  (Pb),  in  sheet  or  granulated  form,  is  used  prin- 
cipally in  the  assay  of  silver  ores.  It  acts  as  a  basic  flux, 
and  a  solvent  or  wash  for  the  precious  metals.  The  sheet 
form  is  useful  in  cupelling  gold  and  silver  beads,  and  in  the 
bullion  assay.  The  granulated  is  essential  in  the  scorifica- 
tion  assay. 

It  can  be  obtained  pure  by  decomposing  the  best  white 
lead  by  charcoal,  and  granulating  or  fusing  in  bars,  as  the 
case  may  require. 

In  sections  where  granulated  lead  free  from  silver,  or 
white  lead,  cannot  be  obtained,  the  assayer  can  make  his 
own  granulated  lead  from  pig  lead,  poor  in  silver,  by  the 
following  method : — Melt  about  fifty  pounds  of  lead  in 
an  iron  pot  or  crucible,  and  keep  it  just  at  the  melting 
point.  Then  pour  a  ladleful  of  the  melted  lead  into  a 
wooden  bread-tray  which  has  been  well  chalked  on  the  in- 
side. Keep  this  agitated  by  gently  rocking  the  tray  to 
prevent  solidification,  and  when  the  mass  begins  to  get 
pasty,  throw  it  into  the  air  and  catch  it  again  repeatedly 
until  cold,  when  the  metal  will  be  found  to  be  nearly  all 
granulated.  Sift  through  a  twenty -mesh  sieve,  and  what 
does  not  go  through  re-melt.  The  whole  fifty  pounds  can 
be  granulated  in  this  way  in  two  hours.  After  granulation 
sample  well  and  test  about  thirty  to  fifty  grammes  for 
silver,  by  the  scorification  assay.  In  using  the  lead,  the 
silver  contained  in  it  must  be  deducted  from  the  results 
obtained  in  assaying  an  ore. 

NITRE  (potassic  nitrate,  KNO3),  acts  as  a  basic  flux  and 
oxidizing  agent.  It  should  be  finely  powdered,  dry,  and 
assayed  for  its  oxidizing  power.  Charge  : 


44  REAGENTS   AND   CHEMICALS. 

Nitre : . . . 3  gms. 

Charcoal 1     " 

Litharge 2  A.T. 

Soda 1     " 

Place  in  a  Hessian  crucible  and  cover  with  salt.  Fuse  in  a 
hot  fire,  remove,  cool  and  weigh.  The  difference  between 
the  weight  of  the  button  obtained  and  that  given  in  the 
assay  of  charcoal,  divided  by  three,  gives  the  oxidizing 
power  of  nitre  per  gramme. 

POWDERED  LIME  (CaO),  (dry),  and  fluor  spar  (CaF2), 
will  often  be  found  useful  as  basic  fluxes,  especially  in  the 
assay  of  iron  ores.  Magnesia  (MgO),  and  alumina  (A12O3) 
or  kaolin  (Al2O3.2SiO2) — are  also  used,  and  cryolite  (3NaF. 
A1F3)  for  tin  ores. 

As  SULPHURIZING  AGENTS — powdered  sulphur  (S),  pure 
galena  (PbS),  or  sulphide  of  antimony  (Sb2S3),  are  employed. 

CARBONATE  OF  AMMONIA  (ammonic  carbonate,  (NH4)2C03), 
as  a  desulphurizing  agent,  is  used  in  the  decomposition  of 
some  sulphates,  as  sulphate  of  copper,  in  roasting.  It 
should  be  powdered  and  kept  in  a  close  vessel. 

COMMON  SALT  (sodic  chloride,  NaCl),  as  a  cover  and 
wash,  and  as  a  reagent  in  the  bullion  assay,  should  be  al- 
ways kept  on  hand.  The  purer  it  is  the  better,  and  it  must 
also  be  fine  and  dry. 

As  SOLVENTS  AND  PEECIPITANTS — distilled  water  (H2O), 
sulphuric  acid  (H2SO4),  nitric  acid  (HNO3),  hydrochloric 
acid  (HC1),  chloride  of  sodium  (Nad),  nitrate  of  silver  (ar- 
gentic nitrate,  AgN03),  and  sulphuretted  hydrogen  (H2S), 
are  most  frequently  employed. 

The  acids  may  be  purchased  pure.  Nitric  acid  should 
be  free  from  chlorine,  which  can  be  separated  by  the  addi- 
tion of  nitrate  of  silver,  drop  by  drop,  until  a  precipitate 
ceases  to  form.  The  clear  acid,  after  settling,  being  drawn 


THE   PRELIMINARY   TESTING   OF   OKES.  45 

off  with  a  syphon.     Any  excess  of  nitrate  of  silver  should 
be  carefully  avoided. 

Mtrate  of  silver  may  be  made  by  dissolving  pure  silver 
in  nitric  acid  free  from  chlorine  ;  evaporate  to  dry  ness  and 
dissolve  one  part  of  the  salt  in  twenty  parts  of  distilled 
water. 

Sulphuretted  hydrogen  is  best  prepared  from  powdered 
sulphide  of   iron  (ferrous   sulphide,  FeS)   and  dilute  sul- 
phuric acid.     The  gas  being  passed  through  a  second  bot- 
tle filled  with  water  to  wash  it.     Fig.  26  shows  the  appara- 
tus in  position  for  use.     The  glass 
tubes  are  connected  with  small  pieces 
of  rubber  tubing.     The  gas  may  be 
passed  into  the  solution  to  be  pre- 
cipitated, or  a  water  solution  may  be 
saturated,  and  used  at  pleasure.   The 
sulphide  of  iron  can  be  made  by 
heating  scrap  iron  or  borings  to  a 
FIG.  26.  red  heat  in  a  crucible  and  throwing 

in  sulphur.     The  sulphide  produced  may  be  then  fused  or 
broken  up;  complete  fusion  is  unnecessary. 

OTHER  CHEMICALS  and  reagents  will  often  be  found  neces- 
sary if  assays  in  the  wet  way  are  to  be  made,  but  the 
reader  must  be  referred  to  the  list  on  page  189.  The  most 
important  are  arsenic  (As),  arsenide  of  iron  (ferrous  ar- 
senide, Fe2As),  hyposulphite  (Na2H2S2O4),  and  sulphide  of 
sodium  (Na8S). 

PRELIMINARY  TESTING  OF  ORES. 

Before  breaking  up  a  sample  it  should  be  thoroughly 
examined  to  determine,  if  possible,  its  inineralogical  char- 


46  SAMPLING   AND   PULVERIZING. 

acter,  and  if  this  is  impossible  it  should  be  tested  with  the 
blowpipe,  by  the  scheme  of  table  pp.  177-184,  Appendix. 

By  the  result  of  the  blowpipe  assay,  the  assayer  can  set-- 
tie upon  what  method  he  will  pursue,  and  often  save  much 
time.  The  determination  of  the  presence  of  gold  will  de- 
cide the  question  of  crucible  or  scorification  assay.  Arsenic, 
antimony  or  sulphur,  that  of  roasting,  etc.  With  a  lit- 
tle practice  the  assayer  will  seldom  have  to  use  the  blow- 
pipe when  the  specimen  is  in  lump,  the  color,  hardness, 
weight  and  general  appearance  indicating  the  nature  of  the 
ore,  and  consequently  the  method  of  assay  ;  all  powdered 
samples  should,  of  course,  be  examined  under  a  magnifying 
glass  and  tested  by  the  blowpipe. 


SAMPLING  AND  PULVERIZING. 

The  selection  and  preparation  of  the  sample  for  assay 
may  be  called  the  ' '  secret  of  success. ' '  It  is  the  most  im- 
portant operation  which  the  assayer  has  to  conduct ;  and 
unless  the  sample  be  well  taken  his  work  will  be  useless. 

No  matter  how  large  or  how  small  the  amount  of  ore  he 
may  be  called  upon  to  treat,  the  same  care  is  necessary  in 
the  sampling  ;  for  one  portion  may  be  very  rich  and  another 
portion  valueless,  so  far  as  the  metal  sought  for  is  concerned. 
The  sample,  therefore,  taken  for  an  assay,  must  always  be 
an  average  of  all  the  ore. 

The  method  of  sampling  an  ore  depends  upon  its  consti- 
tution : 

a. — The  ore  contains  no  metallic  particles. 

£. — The  ore  contains  metallic  particles. 

In  the  first  case  the  operation  is  comparatively  easy.  If 
there  is  a  large  quantity  of  ore  to  be  sampled,  it  is  broken 


SAMPLING*  AND   PULVERIZING.  47 

up  more  or  less  finely,  the  degree  of  fineness  depending 
upon  the  amount  of  ore  from  which  the  lot  for  assay  is  to 
be  taken  ;  and  is  then  either  thrown  upon  a  sampler,  page 
36,  or  divided  by  piling  it  in  a  heap  and  cutting  it  in 
quarters,  one  of  which  may  be  selected  to  be  again  broken 
up  and  quartered,  and  so  on,  until  a  sample  sufficiently 
small  for  assay  is  obtained  ;  or  an  equal  portion  of  each 
quarter  may  be  taken,  and  the  four  portions  well  mixed, 
broken  up,  thrown  in  a  heap,  and  the  operation  repeated 
until  the  required  sample  is  reached.  If  there  is  only  a 
single  specimen  or  lot  obtained  by  sampling  as  above,  it 
is  better  to  crush  it,  and  pass  it  all  through  a  sixty  or 
eighty-mesh  sieve  ;  the  finer  the  better.  The  pulverized 
ore  is  then  well  mixed  with  a  spoon  or  spatula  on  glazed 
paper,  and  the  amount  for  assay  weighed  out  by  taking  a 
little  here  and  there,  or  dividing  into  quarters  and  taking 
some  from  each  quarter.  Various  mechanical  devices  are 
employed  for  sampling  down  large  quantities  of  ore,  but 
for  most  purposes  the  tin  sampler  described  will  be  founiA 
sufficient.  The  size  of  this  may  be  increased  if  desira- 
ble. 

The  fine  ore  should  never  be  shaken  to  mix  it,  or  poured 
upon  the  scale  pan  directly  from  the  vessel  in  which  it  is 
contained. 

b. — The  ore  contains  metallic  particles. 

The  sample  may  be  selected  from  the  heap  of  ore  in  the 
same  manner  as  described  under  a,  but  a  larger  lot  must 
be  taken  for  assay  and  the  whole  pulverized  and  passed 
through  an  eighty-mesh  sieve,  which  will  divide  the  ore 
into  two  portions  : 

1st.  Sif tings. 

3d.  Metallic  residue. 


48  SAMPLING   AND   PULVERIZING. 

The  siftings  must  be  well  mixed  and  sampled  upon  glazed 
paper,  as  just  described. 

The  metallic  residue  must  be  tested  as  a  whole  and  not 
sampled,  or  if  the  amount  is  large,  can  be  fused  with  pure 
lead,  and  a  weighed  portion  of  the  resulting  alloy  as- 
sayed. 

The  method  of  making  the  assay  and  calculation  of  re- 
sults will  be  given  hereafter. 

Care  must  be  taken  in  preparing  a  sample  that  all  appa- 
ratus employed  is  clean,  especially  the  mortars  and  sieves. 

The  first  can  be  cleaned  by  pulverizing  a  little  sand  in 
them,  or  using  a  pumice-stone  pestle,  and  the  latter  by  rub- 
bing with  a  clean  towel  or  rapping  upon  a  bench. 

The  box  sieve,  (page  35),  will  be  found  very  convenient, 
and  better  than  the  ordinary  kind,  as  it  prevents  the  loss  of 
dust  which  would  alter,  more  or  less,  the  value  of  the  sample. 
The  sieve  should  be  used  for  nothing  but  ores,  and  carefully 
cleaned  after  each  operation. 

To  sample  gold  or  silver  bullion,  chip  from  alternate  cor- 
ners above  and  below  ;  or  else  melt  and  take  the  first  and 
last  pouring.  To  sample  coins :  for  silver,  stamp  out  small 
pieces  from  the  center  and  edge ;  for  gold  coins,  cut  slips 
running  from  the  center  to  the  circumference. 

Sometimes  lead  chips  or  granulated  alloys  are  submitted 
to  the  assayer,  which  call  for  great  care  in  sampling.  Lots 
of  this  kind  should  be  weighed  and  melted  in  a  clean  cru- 
cible, carefully  poured  so  as  to  save  all  the  scum ;  the 
bar  weighed  and  sampled  by  chipping  or  boring,  and  the 
scum  weighed  and  scorified.  The  value  of  the  original 
alloy  per  ton  can  then  be  calculated  in  the  same  way  as  an 
ore  which  contains  metallic  particles. 


WEIGHING   OKE   AND   EE AGENTS.  49 


WEIGHING  ORE  AND  REAGENTS. 

The  ore,  litharge,  test  lead,  oxidizing  and  reducing  agents, 
should  be  weighed  accurately. 

The  ordinary  fluxes  may  be  weighed  approximately,  still 
it  is  better  to  weigh  close,  as  more  uniform  results  are  ob- 
tained. 

The  same  pans  of  either  the  flux  or  ore  balance  should 
always  be  used  for  the  weights,  and  the  latter  must  be 
handled  with  the  pincers  provided  for  that  purpose.  The 
ore  scales  should  be  kept  free  from  dust,  and  be  adjusted 
before  each  weighing,  for  next  to  the  sampling,  the  weigh- 
ing of  the  ore  is  most  important. 

When  a  number  of  charges  of  the  same  ore  are  to  be 
weighed,  weigh  out  the  fluxes  first,  and  then  add  the  ore 
in  order.  In  this  way  the  work  will  be  greatly  facilitated. 

Instead  of  weighing  the  pure  granulated  test  lead,  it  can 
be  measured.  A  very  simple  and  good  test  lead  measure  is 
a  glass  tube  about  £  of  an  inch  in  diameter,  in  which  a  cork 
is  fitted  to  slide  up  and  down ;  the  tube  being  graduated 
for  known  weights.  As  far  as  possible  glazed  paper  or  watch 
glasses  should  be  used  in  weighing,  to  prevent  substances 
from  touching  the  scale  pan,  especially  in  employing  the 
quantitative  analytical  balance. 

If  the  substance  is  one  w^hich  is  liable  to  absorb  moisture 
from  the  air  it  should  be  weighed  between  watch  glasses, 
fastened  with  a  clip.  Cyanides  must  never  be  weighed 
upon  the  pan  direct. 

The  balance  pans  of  the  bullion  and  quantitative  balance 
should  never  be  handled  with  the  fingers  or  set  upon  a  rough 
surface. 


50  CALCINATION   AND   BOASTING. 


CALCINATION  AND  ROASTING. 

In  calcination  the  object  is  to  drive  off  moisture,  while  in 
roasting  the  operation  is  conducted  in  such  a  manner  as  to 
ensure  oxidation,  and  the  elimination  of  sulphur,  arsenic, 
antimony,  etc.  To  calcine  a  substance  it  is  not  necessary 
that  the  air  should  have  free  access,  or  that  the  material 
treated  be  constantly  stirred.  For  calcination  a  high  tem- 
perature is  seldom  necessary,  212°-220°  F.  being  sufficient. 
To  conduct  the  operation,  crucibles  will  be  found  the  most 
convenient  vessels. 

For  roasting,  combustion  must  take  place,  and  conse- 
quently the  vessels  employed  must  be  open  and  flat  to  allow 
the  oxygen  of  the  air  to  act  freely.  The  ore  must  be  stirred 
continually,  and  when  easily  fusible,  be  mixed  with  some 
substance  to  prevent  agglutination.  Charcoal,  graphite,  or 
sand  may  be  used  for  this  purpose.  The  heat  should  be  low 
at  first,  and.  raised  toward  the  end  of  the  operation,  and  in 
some  cases  chemicals  mixed  with  the  mass  hasten  the  pro- 
cess, and  render  it  more  complete,  as  in  the  addition  of 
carbonate  of  ammonia  in  roasting  copper  ores,  which  de- 
composes any  sulphates  which  may  have  been  formed.  The 
operation  may  be  performed  on  a  crucible  furnace  in  an  iron 
pan  lined  with  chalk  or  oxide  of  iron  ;  or  in  an  open  vessel 
like  a  scorifier,  (Fig.  10)  in  a  muffle  furnace.  In  any  case 
tbe  draft  of  air  should  be  strong,  as  the  fumes  are  inju- 
rious ;  the  ore,  however,  must  not  be  blown  out. 

A  very  nice  stirrer  for  this  operation  can  be  made  from  a 
piece  of  ordinary  wire,  by  doubling  it  and  bending  down 
the  loop  like  a  small  hoe,  the  ends  of  the  wire  being  twisted 
together  to  form  a  handle. 


REDUCTION  AND   FUSION.  51 


REDUCTION  AND  FUSION. 

Reduction  is  simply  the  removal  of  the  oxygen  from  the 
body  acted  upon  ;  generally  by  the  action  of  substances 
having  a  stronger  affinity  for  it. 

The  operation  of  reduction  is  usually  accompanied  by 
fusion,  which  is  simply  melting,  although  they  may  act  in- 
dependently of  each  other.  Reduction  and  fusion  are  car- 
ried on  in  crucibles,  scorifiers,  etc. 

The  heat  required  is  higher  than  that  necessary  for  the 
foregoing  operations,  consequently  the  draft  should  be 
stronger,  and  for  this  reason  wind  furnaces  are  employed. 
Fusion  is  sometimes  a  preliminary  step  to  oxidation  and 
sublimation. 

To  perform  the  operation  of  reduction  in  a  muffle  fur- 
nace, the  muffle  must  be  partially  filled  with  charcoal,  and 
the  mouth  closed. 

DISTILLATION  AND  SUBLIMATION. 

Distillation  may  be  divided  into  two  cases  : 

a. — When  a  solid  is  acted  upon. 

b. — When  a  liquid  is  acted  upon. 

The  product  is  generally  liquid. 

Sublimation  is  similar  to  distillation,  but  the  product  is 
solid. 

Both  operations  may  be  conducted  in  flasks,  retorts,  or 
crucibles  ;  but  usually  in  the  operation  of  distillation  a 
cooled  condenser  is  necessary,  as  in  the  process  of  making 
distilled  water.  The  term  "destructive  distillation"  is 
used  where  the  body  acted  upon  undergoes  decomposition. 


SCOKIFICATION  AND   CUPELLATION. 


SCORIFICATTON  AND  CUPELLATION. 

Scorification  and  cupellation  include  a  combination  oi 
fusion,  roasting  and  sublimation,  the  difference  being,  that 
in  the  latter  case  the  volatile  compounds  formed  are  absorbed 
by  the  cupel,  while  in  the  former  they  form  a  slag.  Both 
will  be  described  in  detail  hereafter.  (See  assay  of  silver 
ores.) 

INQUARTATION  AND  PARTING. 

Under  this  head  comes  the  separation  of  alloys,  and  the 
treatment  of  the  buttons  from  the  gold  and  silver  assay. 

Inquartation  is  the  process  of  alloying  gold  with  silver  to 
form  a  more  soluble  alloy,  while  parting  is  the  separation  of 
the  metals  by  treatment  with  acids. 


WEIGHING  BEADS  AND  BULLION. 

This  operation  must  be  conducted  with  the  greatest  care, 
and  the  balance  adjusted  both  before  and  after  weighing. 
Before  weighing,  the  bead  or  bullion  should  be  well  cleaned 
with  a  small  brush.  To  weigh  the  buttons  of  the  base 
metals  the  ore  scales  are  sufficiently  accurate ;  but  for  weigh- 
ing silver  and  gold,  the  bullion  balance  must  be  employed. 
The  weights  should  be  counted  on  the  pan,  also  the  vacant 
spaces  in  the  box  as  a  check. 

It  is  best  to  keep  the  bullion  balance  in  a  separate  room 
from  the  laboratory,  where  it  will  be  free  from  dust  and 
fumes.  It  should  also  stand  upon  a  firm  shelf,  to  prevent 
shaking.  In  weighing  a  substance  do  not  use  the  weights 


TABULATING   RESULTS.  53 

at  random,  but  find  the  nearest  single  weight,  and  add  the 
others  in  regular  order,  until  the  required  combination  is 
reached. 

In  duplicate  assays  the  buttons  should  balance  each 
other,  or  very  nearly  so. 

To  facilitate  the  weighing  out  of  pure  silver  in  the  bul- 
lion assay,  Mr.  W.  S.  Ward  of  the  U.  S.  Assay  Office,  in 
the  city  of  New  York,  has  devised  a  series  of  standard 
disks,  which  run  from  fifty  to  five  hundred  milligrammes, 
and  by  combining  one  or  more  almost  any  desired  weight 
can  bo  obtained,  thus  saving  labor  and  time.  When  obtain- 
ing a  weight,  the  door  of  the  balance  should  be  kept  closed, 
and  the  number  of  divisions  marked  by  the  needle  observed, 
and  on  which  side  of  the  centre-line  they  are.  Each  division 
counts  1-10  of  a  milligramme  on  the  second  swing, and  the 
total  can  be  either  added  or  deducted  from  the  weights  in  the 
pan,  as  the  case  may  be  ;  if  the  button  is  heaviest,  add  ;  if 
lightest,  subtract.  On  the  quantitative  balance  the  rider 
indicates  milligrammes  and  fractions  of  the  same,  so  that 
in  obtaining  the  final  weight  after  the  pans  are  nearly  bal- 
anced, the  door  can  be  closed  and  the  rider  adjusted  by 
means  of  the  rod  from  the  right-hand  side.  Never  lean  on 
the  balance  shelf  or  leave  the  rider  on  the  beam.  The 
first  may  throw  the  balance  out  of  adjustment ;  the  second, 
cause  error  in  the  next  weighing. 

TABULATING   RESULTS. 

REPORTING. — In  making  an  assay  each  result  should  be 
noted  as  obtained,  and  nothing  left  to  memory.  Care  should 
also  be  observed  in  arranging  and  reporting.  To  facilitate 
this,  a  series  of  blanks  will  be  found  on  pages  155-162,  from 
which  a  choice  can  be  made. 


54  TABULATING    RESULTS. 

The  report  should  be  made  as  simple  and  comprehensive 
as  possible,  and  written  in  terms  which  a  business  man  can 
understand. 

It  should  also  indicate  in  the  case  of  gold  and  silver,  the 
ounces  Troy  to  the  ton  Avoirdupois,  and  the  value,  in 
gold,  per  ton  of  ore.  Gold  being  taken  at  $20.67  per  oz. 
Troy.  Silver  variable ;  the  value  by  the  old  U.  S.  standard 
being  $1.29  per  oz. 

Base  metals,  such  as  lead,  antimony,  copper,  etc.,  are  re- 
ported in  percentage.  Gold  and  silver  alloys  are  reported 
upon  as  to  fineness,  or  the  number  of  parts  of  each  metal 
in  a  thousand  of  alloy. 


PART  II. 

BEY  OR  FIRE  ASSAYS, 


ERSITY 


LEAD.  57 


LEAD.        Symbol-  Pb. 

SOTJECES. — The  principal  ores  of  lead  are  : 

Galena,  sulphide  (PbS) Pure=86.6  lead 

Minium,  oxide  (Pb3O4) "    =90.       " 

Cerussite,  carbonate  (PbCO3) "    =77.52  " 

Anglesite,  sulphate  (PbSO4) "    =68.31  " 

Pyromorphite,    phosphate     and    chloride 

(3Pb3PA  +  PbCl2) "    =76.36  " 

Lead  also  enters  into  the  composition  of  many  other  min- 
erals, but  they  do  not  occur  in  sufficient  abundance  to  be 
classed  as  workable  ores. 


ASSAY. — The  assay  of  lead  may  be  performed  either  in 
the  crucible  or  muffle  furnace.  The  methods  of  treating 
varying  with  the  ores.  The  object  of  the  assayer  being  in 
all  cases  to  decompose  the  ore  treated,  and  obtain  a  button 
of  lead  by  slagging  off  the  gangue  and  other  impurities. 

Methods  applicable  to  sulphides,  sulphates,  etc. : 

1ST.  3D.  3D. 


Ore lOgms. 

Black  Flux    )        „-     (e 

Substitute      }   ' 

3  Loops  Iron  Wire, 

Points  down. 

Salt Cover. 


Ore 10  gins. 

Soda,  Bi-Carb.  ...30     " 

Argol 2     " 

2  Iron  Nails  / 
Points  down.  \ 
Salt Cover. 


Ore lOgms. 

Ferrocyanide 
of  Potassium — 
dry  10-15  " 

Cyanide  of  Potas- 
sium  5-10  " 

Salt..  ..Cover. 


The  charges  should  be  well  mixed,  transferred  to  a  cru- 
cible, and  covered  with  salt.  The  wires  or  iron  nails  being 
placed  in  such  a  manner  that  they  can  be  drawn  out  quickly 
after  fusion.  A  little  carbonate  of  soda  in  addition  to  the 


58  FIKE  ASSAYS. 

fluxes  given  in  the  third  method,  sometimes  gives  a  better 
slag. 

The  crucible  must  be  covered  while  in  the  fire  and  dur- 
ing the  process  of  cooling. 

In  the  first  and  second  methods  a  double  sulphide  of  soda 
and  lead  is  formed,  which  is  acted  upon  by  the  iron  present ; 
the  carbon  acting  also  as  a  reducing  agent.  In  the  third 
method  the  ore  is  desulphurized  and  reduced  by  the  action 
of  the  cyanide  and  also  by  the  iron  in  the  ferrocyanide. 

4TH. 

Ore 10  gms. 

SodaBi-Carb 20    " 

Argol 5    " 

Flour 2    " 

Borax  (fused) 1     " 

The  ore  and  first  three  fluxes  are  mixed  and  placed  in  a 
small  Hessian  crucible,  which  will  go  into  the  muffle  of  the 
cupel  furnace.  The  borax  is  then  added,  and  three  nails  or 
two  pieces  of  iron  wire  bent  into  the  form  of  hairpins  stuck 
into  the  mass ;  after  which  a  cover  of  salt  J-inch  thick,  is 
packed  upon  the  whole  charge,  and  the  crucible  covered. 

Several  assays  can  be  run  in  a  muffle  at  once,  but  care  in 
heating  should  be  observed.  The  muffle  should  be  at  a 
bright  cherry-red  when  the  assays  are  introduced,  and 
the  heat  raised  until  the  salt  cover  fuses.  This  will  take 
about  twenty  minutes,  after  which  the  muffle  is  made  white 
hot  for  about  ten  minutes,  when  a  perfectly  fluid  fusion  is 
obtained.  The  assays  are  then  withdrawn,  the  wires  care- 
fully taken  out,  the  crucibles  tapped  gently,  and  the 
contents  poured  into  a  mould.  This  operation  must  be 
performed  carefully  and  quickly,  to  prevent  solidification 
of  the  slag.  The  iron  and  carbonaceous  material  act  as 
explained  in  the  preceding  methods. 


LEAD.  59 

STH. 

Ore 10  gms. 

Cyanide  of  Potassium 
25  to  30    " 

Salt cover. 

Fuse  in  a  moderate  fire  twelve  to  fifteen  minutes,  keep 
ing  the  crucible  covered  while  in  the  fire  and  cooling. 

The  cyanide  of  potassium  takes  the  sulphur  from  the  lead 
forming  a  sulpho-cyanide  of  potassium. 
Methods  applicable  to  oxidized  ores,  carbonates,  etc. 

1ST. 

Ore 10  gms. 

Argol 5     " 

SodaBi-Carb 20    " 

Salt cover. 

Mix  well  and  heat  slowly  for  about  twelve  minutes,  and 
then  strongly  until  in  complete  fusion.  Remove  from  the 
fire,  cool  and  break. 

The  argol  in  this  case  acts  as  the  reducing  agent,  owing 
to  its  carbon. 

For  treatment  of  cupel  bottoms  add  ten  grammes  borax 
glass. 

3D. 

Ore 10  gms. 

Black  Flux  Sub...  35    " 

Argol 2    " 

Salt cover. 

Fuse  in  a  hot  fire,  and  in  all  cases  where  the  material 
treated  contains  substances  fusible  with  difficulty,  borax 
glass  must  be  added  to  facilitate  the  fusion. 

The  lead  assay  is  not  accurate  for  several  reasons,  chiefly 
because  of  the  volatility  of  the  lead,  and  the  presence  of 
substances  which  alloy  with  the  button. 

Antimony  and  zinc  in  an  ore  interfere  with  the  as- 
say ;  as  the  first  will  generally  be  found  with  the  lead, 


60  FIEE  ASSAYS. 

while  the  zinc,  though  partially  driven  off,  carries  lead 
with  it. 

When  much  antimony  is  present,  the  following  method 
may  be  employed,  (Mitchell,  pages  379-380),  with  approxi- 
mate results. 

Ore 10  gms. 

Carb.  of  Potash  or  Soda.. 35    " 

Saltpetre 1    " 

Salt cover. 

The  assay  is  performed  in  a  muffle  furnace,  and  requires 
about  thirty  minutes  for  fusion,  then  ten  minutes  slow  cool- 
ing, which  is  done  by  opening  the  door  of  the  muffle,  and 
decreasing  the  heat.  Finally  finishing  with  closed  muf- 
fle, and  a  high  heat  for  ten  minutes,  when  the  crucibles  are 
removed,  cooled  and  broken.  Most  of  the  antimony  re- 
mains in  the  slag.  This  method  requires  care  and  practice. 
Very  often  in  making  an  assay  in  the  muffle  the  crucibles, 
being  small  at  the  bottom,  fall  over.  To  avoid  this,  make  a 
little  platform  of  clay  for  each  crucible. 

Lead  slags  can  be  assayed  by  fusing  the  pulverized  slag 
with  soda  and  charcoal — charge  : 

Slag 20  gms. 

Argol 10    " 

Soda,  Bi-Carb 40    " 

2  Iron  Nails,  points  down. 
Salt cover. 

The  assay  is  conducted  in  the  same  way  as  in  the  treat- 
ment of  ores. 

REMAKKS. — Pure  galena,  treated  by  the  foregoing  meth- 
ods, for  sulphides,  gave  the  following : 


ANTIMONY.  61 

METHOD.  RESULT. 

No.  1 78.4  and  78.6 

"    2 73.       "     73.4 

"    3 78.5     "     79.1 

The  assay  by  cyanide  gives  lower  results,  but  cleaner 
buttons,  and  is  to  be  recommended. 

The  yield  by  muffle  assay  is  high,  duplicates  agreeing 
within  two  per  cent,  and  the  button  being  clean  and  malle- 
able. 

The  first  method  for  carbonates  gives  results  varying 
from  1  to  2  per  cent.,  but  is  better  than  the  second. 

The  method  by  ferrocyanide,  although  given,  is  not  re- 
commended, as  the  buttons  nearly  always  contain  iron. 

A  loss  of  lead  is  sustained  in  all  the  above  processes,  by 
the  volatility  of  this  metal  and  its  oxide ;  for  this  reason 
all  assays  of  lead  ores,  should  be  made  at  as  low  a  tempera- 
ture as  is  compatible  with  perfect  fusion,  and  the  assay 
should  not  be  left  in  the  furnace  longer  than  is  actually 
necessary. 


ANTIMONY.         Symbol— Sb. 

SOURCES.  —  The  principal  ore  of  antimony  is  the  sul- 
phide— called  stibnite,  or  grey  antimony  ore  (Sba  S3) — which 
contains,  when  pure,  71.80  per  cent,  of  metal.  Antimony 
is  also  found  native  alloyed  with  other  metals,  and  in  com- 
bination with  oxygen. 

ASSAY. — In  the  assay  of  antimony  ore,  the  assayermay 
be  required  to  determine  one  of  two  things. 

a.  The  pure  sulphide  of  antimony  (antimonium  crudum), 
which  the  ore  may  contain. 


62  FIBE  ASSAYS. 

b.  The  metallic  antimony  (regains  of  antimony),  which 
the  ore  may  yield. 

a.  Determination  of  the  snlphide.     As  sulphide  of  anti- 
mony fnses  at  a  low  red  heat,  it  is  not  changed  in  its  char- 
acter if  the  air  is  excluded,   so  that  the  following  method 
may  be  adopted  : 

Charge  the  broken  ore  into  a  crucible  the  bottom  of  which 
is  perforated,  and  just  fits  into  a  second  crucible  about  half 
its  depth.  Then  cover  and  lute  the  lid  and  the  joint  be- 
tween the  two  crucibles  with  fire  clay  and  sand.  The  upper 
crucible  only  should  be  heated,  and  to  effect  this  the  lower 
can  extend  into  the  ash-pit  of  the  furnace,  being  supported 
by  an  inverted  crucible  or  a  brick. 

The  sulphide  of  antimony  will  melt  and  collect  in  the 
lower  crucible,  while  the  silicious  and  earthy  matter  re- 
mains in  the  upper. 

b.  Determination  of  metallic  antimony.     1st.  The  ore  is 
in  the  state  of  oxide. 

Ore 10  gms. 

Black  Flux  Sub.... 25    " 

Argol 2    " 

Charcoal  and  salt . . .  cover. 

This  assay  is  conducted  in  the  same  manner  as  for  lead, 
only  the  heat  must  be  regulated  with  more  care,  and  the 
assay  taken  from  the  fire  as  soon  as  finished  ;  the  cover  be- 
ing left  on  the  crucible  while  cooling. 

The  flour  in  the  black  flux  substitute,  and  the  argol, 
act  as  the  reducing  agents,  metallic  antimony  being  pro- 
duced. 

2d.  The  ore  is  a  sulphide. 


ANTIMONY.  63 

Ore 10  gms. 

Cyanide  of  Potassium, 

35-40    " 
Salt cover. 

The  charge  should  be  well  mixed,  the  heat  low,  and 
the  operation  performed  quickly  ;  observing  the  same  pre- 
cautions in  cooling  as  in  the  preceding  method. 

REMARKS. — The  result  obtained  in  assaying  for  antimony 
cannot  be  accepted  as  the  correct  amount  of  metal  in  the 
ore ;  it  only  represents  the  possible  yield,  as  the  button 
often  contains  some  other  metals,  which  have  been  reduced 
with  the  antimony  in  the  ore,  when  the  latter  is  not  pure. 
It  should,  therefore,  be  tested  for  iron,  etc.,  alloyed  with 
the  antimony.  The  button  should  be  cleaned  by  washing, 
and  not  hammered,  to  detach  the  slag,  as  it  is  brittle. 

When  much  iron  and  silicious  matter  is  contained  in  the 
ore,  the  method  for  the  determination  of  the  sulphide  does 
not  give  good  results.  Two  assays  of  impure  stibnite  gave 
44.5  and  44.2  per  cent. 

To  separate  from  foreign  metals,  break  the  button  and 
dissolve  in  concentrated  nitric  acid,  which  converts  the  an- 
timony into  antimonic  acid,  which  is  insoluble.  Filter, 
wash,  dry,  and  ignite  in  a  porcelain  crucible  ;  the  weight 
found  multiplied  by  0.7922  gives  the  metallic  antimony. 
Practically  it  is  not  necessary  to  treat  the  buttons  from  the 
fire  assay,  as  the  loss  by  volatilization  more  than  counter- 
balances the  impurities  in  the  button. 

For  some  impure  ores  a  very  large  charge  of  cyanide 
(say  50-60  gms.),  and  a  quick,  hot  fire  has  been  found  to 
give  good  results. 


64  FIEE  ASSAYS. 

GOLD  AND  SILVER.          Symbols— An.  and  Ag. 

SOURCES. — All  substances  containing  gold  and  silver  may, 
for  the  purposes  of  the  assayer,  be  divided  into  two  classes  : 

Class  1st.  Minerals  or  ores,  including  incidental  indus- 
trial products. 

Class  2d.  Metallic  gold  and  silver,  and  alloys,  native  or 
artificial. 

Metallic  gold  occurs  in  nature  in  sufficient  abundance 
to  have  great  commercial  value.  It  is  found  com- 
monly in  a  quartzose  gangue,  and  nearly  always  associated 
with  one  of  the  following  minerals  :  Iron  and  copper  py- 
rites, mispickel  or  arsenical  pyrites,  blende,  and  galena. 
There  are  also  compounds  with  tellurium,  and  native  alloys. 
(See  pages  146-147.) 

The  principal  sources  of  silver  are  silver  glance,  stephanite, 
pyrargyrite,  kerargyrite,  native  silver,  galena  and  argentife- 
rous copper  ores.  But  as  many  minerals  contain  silver  in 
greater  or  less  quantity,  for  the  convenience  of  the  assayer, 
a  complete  list  has  been  arranged  on  pages  145-146. 

The  assay  for  gold  and  silver  therefore  comprises : 

a.  Assay  of  ores. 

b.  Assay  of  alloys. 

According  as  we  have  material  of  the  1st  or  2d  class. 


••a 


a.  ASSAY  OF  OEES. — Assays  of  gold  and  silver  ores  are 
made  in  almost  the  same  manner,  so  that  a  general  descrip- 
tion will  answer  for  both.  They  embrace  the  following  steps : 

1st.  Preparation  of  the  sample.  2d.  Collection  of  the 
gold  and  silver  in  a  lead  button.  3d.  Cupellation  of  the 
lead  button.  4th.  Weighing  the  bead.  5th.  Inquartation, 
parting,  and  annealing  or  cupelling  of  the  gold  residue. 
6th.  Weighing  the  gold. 


GOLD   AND   SILVER.  65 

PREPARATION  OF  THE  SAMPLE. — Extra  care  must  be  ob- 
served in  sampling.  (See  page  46.) 

THE  COLLECTION  OF  GOLD  AND  SILVER  IN  A  LEAD  BUTTON 
Is  effected  in  a  crucible  or  scorifier,  whence  two  methods  of 
assay:  (a.)  Crucible  assay,  (b.)  Scorilication  assay. 

The  former  is  applicable  to  nearly  all  ores.  The  latter  to 
rich  silver  ores  and  telluride  gold  ores  ;  it  is  not  safe  to  use 
this  method  for  all  gold  ores,  as  a  very  slight  error  may 
make  a  great  difference  in  the  results,  because  of  the  small 
quantity  of  ore  necessarily  employed. 

(a.)  Crucible  Assay. — An  ore  of  gold  or  silver  is  com- 
posed of  precious  metals,  gangue,  oxides,  sulphides,  etc. 
To  collect  the  precious  metals  the  ore  is  mixed  with  lith- 
arge, suitable  fluxes  and  oxidising  or  reducing  agents,  and 
fused  in  a  crucible.  The  litharge  is  reduced  to  metallic 
lead,  seizes  upon  the  precious  metals,  and  collects  at  the 
bottom  of  the  crucible,  while  the  foreign  materials  form 
with  the  fluxes,  a  fusible  slag  above.  The  crucible  is 
poured,  or  broken  when  cold,  and  the  button  detached 
from  the  slag  by  hammering  it  on  an  anvil. 

The  charge  :  The  weight  of  ore  taken  depends  upon  its 
probable  richness  or  poverty,  since  it  is  required  to  obtain 
finally  a  bead  of  precious  metal  for  weighing.  As  a  rule  it 
is  usual  to  take  one-third  to  one  assay  ton  for  silver,  and 
one,  two,  or  even  four  assay  tons  for  gold  ores.  All  ores  re- 
quire the  following  reagents  :  Argol,  charcoal,  or  an  oxidiz- 
ing agent  (nitre),  with  invariably  a  cover  of  salt.  Borax, 
silica,  and  other  reagents  are  useful  at  times,  but  their 
employment  must  be  left  to  the  judgment  of  the  assayer, 
guided  by  the  properties  of  the  reagents,  and  the  com- 
position of  the  ore.  It  is  well  to  bear  in  mind  that  for 
basic  impurities,  an  acid  flux  is  used,  and  for  an  acid  gan- 


66  FIRE   ASSAYS. 

gue  a  basic  flux.  Unless  the  charge  of  ore  be  very  large, 
as  a  rule,  employ  50  grammes  of  litharge,  and  the  same 
amount  of  carbonate  of  soda  as  of  ore.  These  propor- 
tions may  be  modified  according  to  the  composition  of 
the  ore.  The  amount  of  nitre  depends  upon  the  reduc- 
ing power  of  the  ore.  It  is  added  to  lessen  the  size  of  the 
button. 

Size  of  the  lead  button :  There  are  two  limits  to  the 
size  of  the  button.  (1st.)  It  must  be  large  enough,  or 
sufficient  litharge  must  be  reduced  throughout  the  mass 
to  collect  all  the  precious  metals.  (3d.)  There  should  not 
be  an  excess  of  lead,  which  would  occasion  a  loss  of  sil- 
ver in  cupellation.  A  button  of  fifteen  or  twenty  grammes 
is  the  best  size  for  a  weight  of  ore  from  one- third  to  four 
assay  tons,  and  is  convenient  for  cupellation.  A  button 
too  large  for  cupellation  can  be  made  smaller  by  scorify- 
ing. The  reducing  power  of  an  ore  is  due  to  the  presence 
of  sulphur,  arsenic,  antimony,  zinc,  etc. 

PRELIMINARY  ASSAY  OF  ORES. — Warm  the  crucible  be- 
fore placing  it  in  the  fire,  which  should  be  bright,  and 
effect  the  fusion  in  the  shortest  possible  time.  When  the 
the  contents  of  the  crucible  are  in  quiet  fusion,  withdraw, 
'tap,  cool  and  break.  The  charge  of  ore  is  as  follows  : 

Ore 2  gms. 

Litharge 25    " 

SodaBi-Carb 10    " 

Salt cover. 

Three  cases  may  arise  here.     Two  grammes  may  yield  : 
1st.  No  lead,  or  less  than  three  grammes. 
2d.  Three  grammes  of  lead. 
3d.  More  than  three  grammes. 


GOLD  AND   SILVEE.  67 

Let  us  suppose  we  take  for  assay  £  A.  T.  of  silver  ore, 
and  the  reducing  power  of  two  grammes  of  ore  is  1.5  gms. 
lead,  i  A.  T.,  or  ten  grammes  of  ore,  (about),  will  reduce 
7.5  of  lead,  and  as  the  required  button  is  fifteen  grammes, 
we  must  add  enough  argol  or  charcoal  to  reduce  7.5  gms. 
in  addition  ;  taking  argol  as  8.5,  we  shall  require  7.5-^-8.5 
=0.882,  say  one  gramme,  or  charcoal  7. 5-^28 =0.268  say  i 
of  a  gramme. 

If  the  reducing  power  corresponds  to  the  third  case,  divide 
the  excess  of  lead  by  the  oxidizing  power  of  nitre,  the  quo- 
tient will  show  how  much  nitre  is  needed.  In  the  second 
case,  ten  grammes  of  ore  would  reduce  a  button  of  fifteen. 
Experience  will  often  enable  the  assayer  to  judge  of  the 
reducing  power  without  extra  assay,  by  noting  the  approxi- 
mate amount  of  sulphides  contained  in  the  ore  before  pul- 
verizing the  same. 

After  preparing  a  charge  from  the  data  obtained  by  this 
assay,  it  should  be  fused,  and  the  slag  carefully  examined 
before  running  a  duplicate,  so  that  silica  or  borax  may  be 
added  if  the  slag  is  basic,  or  any  mistakes  as  to  reducing 
power  corrected. 

ROASTING. — Ores  containing  a  large  amount  of  sulphur, 
arsenic,  antimony,  or  zinc,  should  be  roasted.  In  the  former 
case,  if  the  ore  is  not  roasted  there  will  be  danger  of  the 
formation  of  oxysulphurets,  which,  though  fusible,  are  not 
decomposed  at  a  white  heat,  and  enter  the  slag  carry- 
ing silver  with  them.  A  large  quantity  of  nitre  is  lia- 
ble to  boil  over  ;  even  should  this  not  occur,  the  evolu- 
tion of  vapors  puffs  up  the  mass,  and  lead  may  be  left 
adhering  to  the  sides  of  the  crucible.  Arsenic  and  anti- 
mony produce  arseniates  and  antimoniates,  which  carry 


68  FIKE  ASSAYS. 

silver  into  the  slag.  Zinc  also  increases  the  loss  of  silver 
by  volatilization,  and  in  the  slag. 

The  ore  may  be  roasted  conveniently  in  a  cast-iron  pan 
over  the  furnace.  The  pan  should  be  coated  with  red  ochre, 
or  chalk,  which  protects  it  and  prevents  loss  of  ore. 

The  weighed  sample  must  be  spread  over  the  pan,  and 
stirred  until  all  danger  of  fusion  is  past.  The  ore  must  be 
heated  gradually,  not  above  a  dull  red  for  some  time,  and 
finally  to  a  full  red  or  higher  heat.  Too  high  a  temperature 
at  the  outset  causes  the  fusion  of  sulphides  and  the  formation 
of  matter  troublesome  to  roast.  A  rapid  disengagement  of 
arsenic,  antimony,  or  zinc  will  also  causo  a  mechanical  loss 
of  silver.  Should  fusion  occur,  it  is  better  to  weigh  out  a 
fresh  portion  of  ore  and  roast  it  again.  The  operation  may 
be  considered  finished  when,  after  keeping  the  pan  at  a  full 
red  heat  for  some  time,  no  fumes  can  be  perceived. 

If  copper  pyrites  be  present  after  roasting,  cool  and  mix 
some  carbonate  of  ammonia  with  the  ore.  Cover  and  heat 
the  pan  until  fumes  have  ceased.  The  sulphates  are  con- 
verted into  volatile  sulphate  of  ammonia,  which  passes  off. 

Arsenic  and  antimony  require  the  addition  of  fine  char- 
coal to  reduce  arseniates  and  antimoniates  formed  in  roast- 
ing ;  care  being  taken  to  burn  out  all  the  charcoal.  If  the 
ore  contains  a  fusible  sulphide,  as  antimony  glance  or  gale- 
na, mix  with  some  fine  sand  before  roasting.  Ores  may  be 
roasted  in  the  muffle,  in  the  earthen  saucer  already  men- 
tioned, page  29. 

FUSION. — The  prepared  charge  is  thoroughly  mixed  and 
placed  in  a  crucible.  A  hot  fire  is  employed,  and  the  cruci- 
ble removed  when  complete  fusion  has  taken  place.  This 
requires  from  thirty  to  forty-five  minutes.  The  crucible  is 
tapped  on  the  floor,  poured,  or  broken  when  cold. 


GOLD   AND   SILVER.  69 

(b  )  Scarification  Assay. — The  reagents  for  scorification 
assay  are  pure  granulated  lead,  and  borax  glass.  The  ore 
is  mixed  with  these,  the  mixture  put  in  a  scorifier,  and 
fused  in  a  muffle. 

An  alloy  of  lead  with  the  precious  metals,  and  a  slag 
composed  of  litharge  with  tie  impurities  and  gangue 
of  the  ore  is  formed.  The  proportions  of  lead  and 
borax  will  vary  and  should  be  greater  as  the  gangue  and 
metallic  oxides  are  more  difficult  of  fusion.  The  following 
table  shows  the  proportions  found  by  experience  to  be 
adapted  to  the  different  gangues.  They  are  referred  to  one 

part  of  ore  : 

PARTS  PARTS 

CHARACTER  OF  GANGUE.  TEST  LEAD.  BORAX  GLASS. 

Quartzose 8. 

Basic 8.  0.25—1.00 

Galena 5.6  0.15 

Arsenical 16.  0.10—0.50 

Antimonial 16.  0.10—1.00 

Fahlerz. 12—16  0.10—0.15 

Iron  pyrites 10—15  0. 10— 0.20 

Blende 10—15  0.10—0.20 

In  most  cases  one-tenth  of  an  assay  ton  of  ore  and  thirty 
to  forty  grammes  of  lead  will  be  found  to  work  well.  The 
ore  and  one-half  the  lead  are  mixed  in  the  bottom  of  the  sco- 
rifier, and  the  rest  of  the  lead  poured  over  the  mixture  so  as 
to  form  a  cover.  Two  or  three  lumps  of  borax  glass  the  size 
of  a  pea  being  placed  on  top.  The  charge  of  ore  varies  from 
one-third  to  one-twentieth  of  an  assay  ton  according  to  its 
richness,  and  if  one  scorifier  will  not  contain  it,  weigh  equal 
fractional  parts  for  the  number  required,  rather  than  to 
weigh  the  whole  charge  and  roughly  divide  it  between  the 
scorifiers. 


70  FIKE   ASSAYS. 

Three  distinct  periods  may  be  noted  in  the  working  of 
an  assay.  (1.)  Roasting.  (2.)  Fusion.  (3.)  Scorification. 

A  strong  heat  is  maintained  at  first  to  melt  the  lead.  This 
is  effected  by  closing  the  muffle  and  increasing  the  draft. 
As  soon  as  the  lead  is  fused  the  muffle  is  opened,  and  the 
ore  is  seen  floating  upon  the  surface  of  the  lead.  In  a  large 
muffle  it  is  sufficient  to  place  the  scorifier  in  the  back  part 
first,  and  move  it  forward  when  the  lead  is  fused. 

(1).  The  roasting  commences  and  is  continued  at  a  mod- 
erate heat  until  no  more  fumes  are  seen,  and  the  ore  has 
disappeared. 

(2).  The  heat  is  raised  in  order  to  fuse  all  the  material. 
When  the  fusion  is  complete,  clear  white  fumes  of  lead 
arise  from  the  scorifier,  there  is  a  play  of  colors  across  the 
surface  of  the  lead,  and  the  slag  encircles  the  metallic  bath 
like  a  ring.  The  borax  glass  plays  an  important  part  just 
here,  by  giving  liquidity  to  the  slag,  so  that  it  can  be  thrown 
to  the  side  as  fast  as  formed,  exposing  the  lead  for  oxida- 
tion. If  borax  glass  is  not  added  and  the  ore  contains 
much  gangue  and  is  not  easily  fusible,  the  scorige  will  float 
in  masses  over  the  lead,  impeding  the  oxidation. 

(3).  When  fusion  is  complete  the  heat  is  lowered  to  a 
constant  point,  until  the  ring  of  slag,  which  is  continually 
growing  smaller,  closes  over  the  lead.  Then  the  heat  should 
again  be  raised  to  liquify  the  slag,  and  allow  the  lead  to 
settle,  after  which  the  scorifier  is  removed  from  the  furnace, 
cooled  or  poured.  Hammer  the  button  as  usual.  The 
whole  assay  occupies  from  thirty -five  to  fifty  minutes.  Too 
much  borax  should  not  be  added  at  first ;  it  is  better  to  mix 
only  a  portion  with  the  ore,  and  to  introduce  the  rest  as 
needed  during  the  operation,  wrapped  in  a  small  piece  of 
paper. 


N 

TJK 


GOLD   AND   SILVEK."  71 


GALENA — SPECIAL  METHOD. — It  is  best  to  make  a  scor- 
ification  assay  of  galena.  If,  however,  it  is  desirable  to 
make  a  crucible  assay,  a  charge  of  nitre  and  carbonate 
of  soda  is  employed,  instead  of  roasting  the  ore.  Twenty 
grammes  of  nitre  per  assay  ton  are  required  for  pure  gale- 
na, this  amount  diminishing  as  the  gangue  increases  in 
quantity,  or  the  sulphur  is  lessened.  Employ  the  same 
weight  of  carbonate  of  soda  as  of  ore.  Make  a  prelimi- 
nary assay  with  an  assumed  charge,  and  modify  the  reg- 
ular charge  according  to  the  result. 

THE  LEAD  BUTTON. — The  lead  button  for  cupellation 
must  be  malleable  and  of  the  proper  size. 

A  good  cupel  will  absorb  its  own  weight  of  litharge,  but 
it  is  better  to  use  a  cupel  one-third  as  heavy  again  as  the 
button.  The  cupels  in  ordinary  use  weigh  about  eighteen 
grammes.  If  a  button  be  too  large  it  may  be  reduced 
in  size  by  scorification  ;  there  is  less  loss  in  this  opera- 
tion than  in  cupellation.  A  brittle  button  may  be  due  to 
arsenic,  antimony,  zinc,  or  litharge,  and  must  be  scorified 
before  cupellation,  with  lead  if  necessary.  If  the  button 
contains  copper,  it  must  be  scorified  until  no  more  copper 
can  be  seen  on  hammering.  If  nickel  is  present  the  button 
cannot  be  cupelled  ;  this,  however,  will  rarely  occur. 

CUPELLATION. — This  operation  differs  from  scorification 
in  that  the  scoriae  formed  are  absorbed  by  the  cupel,  leav- 
ing a  pure  bead  of  the  precious  metals. 

It  is  thus  that  we  get  rid  of  small  amounts  of  copper,  iron, 
arsenic,  etc.,  in  the  lead  button.  The  proportion  of  lead 
required  to  carry  off  impurities  varies  according  to  cir- 
cumstances. The  operation  of  cupelling  is  conducted  as 
follows  :  A  cupel  is  wiped  out  with  the  fingers  carefully, 


72  FIKE  ASSAYS. 

all  extraneous  matter  blown  out,  and  then  placed  in  the 
muffle  and  heated  until  of  the  same  temperature  as  the 
latter,  when  the  button  is  gently  placed  in  the  cupel  with 
a  pair  of  forceps.  The  muffle  is  then  closed  by  a  door  or 
a  piece  of  lighted  charcoal,  to  melt  the  lead.  This  done, 
the  muffle  is  opened  and  the  button,  which  at  first  appears 
bright  and  uncovered,  is  soon  coated  with  a  film  of  oxide 
moving  in  luminous  patches  over  its  surface,  and  being  con- 
tinually thrown  toward  the  edge  Avhere  it  is  absorbed  by  the 
cupel.  The  button  gradually  diminishes  in  size  by  oxidation 
and  absorption  and  becomes  more  convex  ;  the  patches  be- 
come larger  and  move  more  quickly  ;  the  last  of  the  lead  is 
absorbed,  and  the  residue  appears  to  revolve  rapidly,  becomes 
very  brilliant,  and  is  suffused  with  the  tints  of  the  rainbow  ; 
then  presents  the  appearance  of  the  precious  metals.  The 
latter  part  of  the  operation  is  called  the  ' '  brightening ' '  of 
the  button.  Should  the  bead  be  large  and  composed  of 
silver,  it  must  be  removed  slowly  from  the  furnace  to  pre- 
vent "  spitting,"  by  which  portions  of  the  metal  are  thrown 
off  and  lost.  In  case  the  bead  is  very  large,  say  one  hun- 
dred to  three  hundred  milligrammes,  it  is  well  to  cover  it 
with  a  hot  cupel.  If  the  bead  is  not  larger  than  the  head 
of  an  ordinary  pin  the  danger  of  spitting  is  slight  and  no 
great  precaution  need  be  taken  in  its  removal. 

Two  causes  have  been  assigned  for  this  spitting.  First, 
That  the  molten  silver  absorbs  oxygen  from  the  atmosphere 
and  gives  it  up  at  the  moment  of  solidifying.  Second,  That 
by  rapid  cooling  a  crust  is  formed  upon  the  outside  which 
contracts  upon  the  liquid  interior.  It  has  been  suggested, 
that  as  the  sprouting  is  caused  by  the  giving  out  of  the 
oxygen  absorbed  when  the  last  traces  of  lead  are  being 
driven  off,  a  piece  of  charcoal  laid  over  the  cupel  during 


GOLD   AND   SILVEK.  73 

this  period  would  act  as  a  preventive,  and  not  interfere 
with  the  cupellatior,. 

It  is  well  to  raise  the  heat  of  the  muffle  just  at  the  time 
of  brightening,  or  to  push  the  cupel  into  the  hotter  part 
to  remove  the  traces  of  lead. 

Silver  is  sensibly  volatile  at  a  high  heat,  and  the  loss 
increases  with  the  temperature.  We  must  avoid  the  two 
extremes  of  a  high  heat  and  quick  work,  and  a  low  heat 
and  prolonged  work.  Of  the  two  the  latter  is  worse.  The 
following  are  indices  of  favorable  working  :  The  muffle  is 
reddish-white,  the  cupel  red,  the  fused  metal  luminous  and 
clear,  the  lead  fumes  rise  slowly,  and  the  litharge  is  com- 
pletely absorbed  by  the  cupeL 

The  heat  is  too  great  when  the  cupels  are  whitish,  when 
the  fused  metal  is  seen  with  difficulty  and  the  scarcely  vis- 
ible fumes  rise  rapidly. 

The  heat  is  too  low  when  the  fumes  are  thick  and  fall, 
and  when  the  unabsorbed  litharge  forms  lumps  and  scales 
about  the  button. 

The  degree  of  heat  may  be  greater  according  as  the  lead 
is  poorer  in  silver.  By  bearing  this  in  mind  the  assayer 
can  often  hasten  the  operation  without  detriment. 

Too  strong  a  current  of  air  cools  the  cupel  and  oxidizes 
the  lead  faster  than  it  can  be  absorbed.  Too  slow  a  cur- 
rent prolongs  the  operation  and  increases  the  loss  by  volati- 
lization. 

Sometimes  the  material  in.  a  cupel  becomes  solidified  in 
the  midst  of  an  operation,  stopping  further  action.  This  is 
called  "freezing,"  and  is  occasioned  by  a  production  of 
litharge  more  rapidly  than  it  can  be  absorbed  by  the  cupel, 
infusible  scoriae  due  to  a  cold  furnace,  or  an  excess  of 
foreign  oxides.  It  can  sometimes  be  remedied  by  rais- 


74  FIKE  ASSAYS. 

ing  the  lieat  of  the  muffle  ;  or  if  the  accident  be  due  to 
foreign  oxides,  an  addition  of  pure  lead  may  be  made  to 
the  assay.  In  either  case  the  results  are  unreliable. 

An  assay  that  has  passed  well,  furnishes  a  bead  well 
rounded,  crystalline  below,  and  readily  detached  from  the 
cupel.  If  the  bead  contains  lead  it  is  brilliant  below,  and 
does  not  adhere  at  all  to  the  cupel.  If  it  exhibits  rootlets, 
the  results  are  inaccurate,  and  must  be  rejected. 

WEIGHING  THE  BEAD. — The  bead  of  gold  and  silver  is 
detached  from  the  cupel  with  pincers,  thoroughly  cleansed 
with  a  small  brush  and  weighed. 

INQUARTATION  AND  PARTING. — The  separation  of  gold 
from  silver  is  termed  parting.  It  is  effected  by  means 
of  nitric  acid,  which  dissolves  the  silver  and  leaves  the 
gold.  It  is  essential  that  a  certain  relation  should  exist 
between  the  amount  of  gold  and  silver  in  the  alloy. 

If  there  be  too  little  silver  it  win  not  dissolve  completely, 
but  Avill  be  so  enveloped  in  the  gold  as  to  escape  the  action 
of  the  acid. 

If  too  much  silver  be  present,  the  gold  obtained  will  be 
so  fine  and  light  as  to  occasion  loss  in  washing. 

The  amount  of  silver  added  should  be  from  two  to  three 
times  the  weight  of  the  gold.  The  assayer  must  judge 
by  the  color  of  the  bead  as  to  the  proportion  of  silver 
contained,  and  if  it  be  too  small  he  must  supply  the 
deficiency  with  pure  silver,  which  is  kept  on  hand  in 
thin  foil.  The  bead  and  silver  are  well  fused  together  to 
effect  complete  distribution  of  the  silver.  The  fusion 
may  be  made  on  charcoal  by  the  blowpipe,  or  by  wrap- 
ping the  bead  and  silver  in  a  cornet  of  lead  foil,  and  cupel- 
ling it. 


GOLD   AND    SILVER.  75 

The  bead  is  then  flattened  on  an  anvil,  and  treated 
in  a  porcelain  capsule  (Fig.  27),  with  nitric  acid,  C.  P. 
FIG.  27.  1.16  sp.  gr.  (21°  Beaume).  Enough  acid  is  added 
to  cover  the  bead  and  heated  gently.  The  acid  must  be  free 
from  chlorine,  which  would  precipitate  the  silver.  When 
all  action  of  the  first  acid  has  ceased,  decant,  and  care- 
fully add  some  fresh  acid  of  1.26  sp.  gr.  (32°  Beaume). 
Heat  for  several  minutes,  pour  off  the  acid  and  wash  thor- 
oughly with  distilled  water,  and  dry  the  residue  of  gold. 
It  is  well  to  apply  a  high  heat  before  attempting  to  remove 
the  gold,  to  render  it  adherent.  The  gold  residue  is  de- 
tached with  a  knife,  transferred  to  a  cornet  of  lead,  cupelled 
and  weighed.  Or  if  perfectly  clean  and  yellow,  weighed 
without  cupellation. 

WEIGHING  THE  GOLD. — The  gold  obtained  is  weighed  as 
described,  and  the  assay  is  completed. 

CALCULATION  OF  RESULTS. — The  milligrammes,  of  pre- 
cious metal  obtained  per  assay  ton  of  ore,  correspond  to 
Troy  ounces  in  the  ton  of  two  thousand  pounds  Avoirdu- 
pois. There  is  therefore  no  trouble  save  in  the  case  of  an 
ore  which  contains  metallic  scales,  and  the  method  em- 
ployed when  such  is  the  case,  can  be  shown  by  an  example. 
The  sample  presented  for  assay  weighs  485  gms.  Pulver- 
ized and  sifted  in  a  box  sieve  (Fig.  18)  it  gave : 

A.  Sifted  ore 480.  gms. 

B.  Metallic  scales 5.      " 

There  will  be  a  little  loss  in  sifting,  but  if  the  operation 

be  done  carefully  it  need  not  be  taken  into  account. 
A.  SIFTED  ORE. — 10  grammes  gave  by  crucible  assay  : 

Gold 4.      mgs. 

Silver,  after  deduction  of  the  silver  in  the  litharge,  14.3       " 


76  TIKE   ASSAYS. 

Hence,  the  total  precious  metal  in  the  sif  tings  is  : 
Gold  ...................................  JX48()=:192  0 


Silver  .................................  X480=  686>4 

B.  METALLIC  SCALES.  —  These  melted  with  lead  gave  a 
button  of,  say  60  gms.,  which  was  rolled  out  and  10  gms. 
taken  for  cupellation,  which  yielded  : 

Gold  ..................................     2.6  mgs. 

Silver  ................................  500.0     " 

Hence,  the  total  precious  metals  in  residue  must  be  : 
Gold  .............................  _jyLx60=     15.60  mgs. 

Silver  ......................  - 


Total  : 
Gold  in  sif  tings  ...............................  192.00  mgs. 

"     "  residue  ...............................  15.60     " 

"     "  ore  taken  ............................  207.60     " 

Hence  : 

J  4S^   X  29.  166  (value  of  an  assay  ton)  =  gold  per  assay  ton 

of  original  ore. 

Silver  in  total  siftings  ........................   686.40  mgs. 

"       "residue  ..............  ...............  3000.00     " 

"       "  ore  taken  ...........................  3686.40     " 

Hence  : 

~AQK~~  X  29.  166  (value  of  an  assay  ton)  =  silver  per  assay  ton 
of  original  ore. 

REMARKS.  —  All  ores  or  minerals  of  gold  or  silver  can  be 


GOLD   AXD   SILVER.  77 

assayed  by  3ither  (a)  crucible,  or  (5)  scorification.  The 
latter  is  preferable  whenever  it  can  be  used,  as  it  yields 
higher  results  and  requires  no  preliminary  assay.  No  oxy- 
sulphurets  are  formed,  or  if  formed,  are  decomposed  during 
the  operation  ;  whereas,  in  the  crucible  assay  they  may  es- 
cape decomposition  even  at  a  white  heat.  It  is  better 
for  zinc  and  copper  ores,  the  action  of  scorification  being 
oxidizing,  that  of  the  crucible  reducing ;  in  the  latter 
case  much  copper  will  enter  the  lead  button  that,  in  the 
former,  would  be  oxidized  and  enter  the  slag.  Instead  of 
roasting,  another  method  for  arsenical  and  antimonial 
ores  is,  ore  1  A.  T.,  litharge  2  A.  T.,  soda  1  A.  T.,  ferro- 
cyanide  of  potassium  35  gms.,  and  a  cover  of  salt.  The 
button  must  be  scorified.  The  matte  over  the  button 
should  be  saved  and  put  in  the  scorifier  as  it  may  carry 
silver. 

In  scorifying  mattes  of  this  kind,  and  ores  which  contain 
much  sulphide  of  iron  and  copper,  the  addition  of  a  little 
nitre  and  soda  bi-carb.  (mixture  of  equal  parts  of  each) 
will  sometimes  make  the  scorification  work  better  and  give 
a  good  slag.  The  mixture  should  be  added  to  the  scorifier 
in  the  furnace  if  the  slag  seems  thick  and  lumpy,  care  be- 
ing taken  not  to  slag  the  scorifier  over  by  adding  too  much. 
Instead  of  the  above  mixture,  a  little  litharge  might  be 
added  with  good  results,  but  as  it  is  likely  to  contain  sil- 
ver it  should  be  weighed  beforehand. 

After  roasting  an  ore  for  crucible  assay,  if  much  iron  is 
contained,  add  more  charcoal  than  is  necessary  for  a  fifteen 
gm.  button,  as  the  ore  has  an  oxidizing  action.  Sometimes, 
to  avoid  roasting,  just  sufficient  litharge  may  be  added  to 
give  the  required  button  of  lead,  but  this  is  not  always 
safe. 


78  FIKE  ASSAYS. 

For  ores  containing,  say  80  oz.  of  silver  to  the  ton,  the  fol- 
lowing crucible  charge  has  been  recommended : 

Ore       i  A.  T. 

Litharge |     " 

Flour 6  gms. 

Soda,  Bi-Carb 50     " 

Five  or  six  Iron  Nails. 
Borax . .  cover  of  about  10     " 

If  much  copper  is  present  in  the  ore,  use  more  litharge  ; 
if  the  sample  contains  lead,  use  less. 

Gold  ores  containing  an  excess  of  sulphide  of  iron  and 
copper  can  be  satisfactorily  assayed  by  the  following 
method : 

Ore 2  A.  T. 

Soda,  Bi-Carb 4     " 

Litharge 2     " 

Black  Flux  Sub 1     " 

Silica 2     " 

Iron  Wire 12  loops. 

Salt cover. 

Mix  the  charge  well  and  fuse  in  a  hot  fire.  The  slag 
should  be  glassy  and  the  button  malleable.  If  any  matte 
is  formed,  collect  and  scorify  down  with  the  button,  adding 
to  the  scorifier  a  little  test  lead  and  borax  glass. 

Alloys  which  contain  gold  and  silver  may  be  fused  in  a 
scorifier  with  pure  lead,  and  the  button  scorified  down  and 
cupelled,  the  resulting  bead  being  carefully  parted  with 
nitric  acid  in  the  usual  way.  In  weighing  the  gold  which 
has  been  parted,  if  not  previously  cupelled,  it  can  be  trans- 
ferred to  the  scale-pan  by  means  of  a  piece  of  pointed 
wood,  great  care  being  observed  not  to  lose  any. 

Ores  of  gold  or  silver  containing  tellurium  can  be  assayed 


GOLD   AND   SILVEE.  79 

by  scorification  or  crucible,  all  difficulty  arising  from  the 
presence  of  this  metal  being  overcome  by  the  use  of  plenty 
of  lead  or  litharge  (a  cover  of  litharge  has  also  been  recom- 
mended). The  amount  must  be  increased  in  proportion  to 
the  richness  of  the  ores.  In  the  case  of  very  rich  ores, 
sixty  to  one  hundred  parts  of  lead  may  be  employed  in 
scorification  with  advantage.  In  such  cases  it  will  be  found 
more  advisable  to  use  the  larger  sizes  of  scorifiers  rather 
than  to  divide  the  charge  up  into  several  smaller  ones. 

If  an  insufficient  quantity  of  lead  is  used,  the  result  will 
be  a  flat  and  ragged  button  after  cupellation,  and  loss  of 
precious  metal  owing  to  its  failure  to  collect  in  one  button. 
The  tellurium  must  be  driven  off  before  the  lead  button  is 
cupelled.  There  is  probably  no  loss  of  gold  from  volatili- 
zation with  tellurium,  but  the  loss  when  it  occurs,  is  from 
the  subdivision  of  the  gold  button  into  minute  particles  on 
the  cupel. 

The  assay  of  gold  and  silver,  if  conducted  carefully,  is 
one  of  great  accuracy.  Duplicates  of  silver  should  agree 
to  within  one-half  ounce  Troy  per  ton  of  two  thousand 
pounds,  and  for  gold  there  should  be  no  difference.  This 
is  true  of  all  ores,  though  some  are  more  difficult  than 
others.  Where  the  difference  is  greater  than  the  above  and 
accuracy  is  required,  a  third  assay  should  be  made.  Tests 
made  in  duplicate  of  type  ores  gave  : 

ORE.                                SILVER.  GOLD. 

Gold  ore,  quartzose. . .  .29.    and  29.2  ozs.  10.4  and  10.4  ozs. 

Poor  Galena 5.4     "      5.4  "  none 

Zinc  Blende 4.3     "      4.3  " 

Arsenical 55.       "    55.  "  trace 

Antimonial 57.       "    57.  "  none 

Impure  mixture 28. 6     k '    28. 6  "  2.4  and    2. 4  ozs. 


80  FIEE   ASSAYS. 

PLATINUM.          &ymbol—'Pt. 

SOURCES. — Platinum  is  found  native  and  associated  with 
a  variety  of  metals,  such  as  palladium,  iridium,  osmium, 
copper,  iron,  gold,  silver,  etc. 

It  occurs  in  alluvial  deposits  in  grains,  and  sometimes  in 
masses. 

ASSAY. — The  assay  of  platinum  ores  may  be  performed 
in  two  ways : 

(a)  By  fusion  with  lead.  (&)  By  solution  and  precipi- 
tation. (See  scheme,  p.  121.) 

(a)  Fusion  with  lead  :  Weigh  and  pulverize  the  sam- 
ple as  finely  as  possible,  then  sift ;  the  metallic  residue  will 
contain  most  of  the  metal  sought  for.  Weigh  the  residue 
and  sif tings  separately. 

1.  Sif  tings — charge  10  gms.  in  a  small  crucible  with 

Litharge 50  gms. 

Borax  glass 15     " 

Soda 30     " 

Charcoal 1     " 

Part  of  the  soda  should  be  mixed  with  the  charge  and 
part  used  as  a  cover.  The  proportion  of  fluxes  may  be 
varied  to  suit  the  gangue,  so  as  to  render  the  slag  as  fusible 
as  possible. 

The  litharge  is  reduced  by  the  charcoal  and  alloys  with 
the  platinum  and  foreign  metals,  save  irid-osmium,  which 
will  be  found  principally  under  the  lead  button.  The  lead 
button  is  then  broken  out,  scorified  with  a  little  borax  glass 
if  too  large,  and  cupelled  at  as  high  a  temperature  as  pos- 
sible in  an  ordinary  bone-ash  cupel  until  it  solidifies.  The 
residue  will  be  platinum,  with  a  little  silver,  gold,  etc.  It 
may  be  purified  by  fusing  in  a  crucible  of  cut  lime,  which 


PLATINUM.  81 

is  heated  by  coal  gas,  the  combustion  being  supported  by  a 
current  of  oxygen. 

The  lead  retained  in  the  unpurified  button  is  about  one- 
eighth  to  one-sixth  of  its  weight. 

2.  Residue — Fuse  directly  in  a  scorifier  with  pure  lead 
and  borax  glass,  cupelling  the  whole  or  a  weighed  portion 
of  the  resulting  button  if  it  be  too  large,  as  in  1. 

REMAKKS. — In  place  of  the  method  used  for  the  sif tings, 
pure  galena  and  iron  wire  might  be  employed,  as  in  the 
assay  for  lead,  other  fluxes  being  added  to  suit. 

In  the  charge  given  for  sif  tings,  twenty  to  thirty  grammes 
of  granulated  lead  in  addition  to  the  litharge  can  be  used 
with  advantage. 

Instead  of  cupelling  the  lead  button  containing  the  plati- 
num, alone,  add  four  to  five  times  the  weight  of  the  button 
in  silver.  This  gives  a  result  free  from  lead.  The  silver 
can  afterwards  be  deducted  in  the  calculation  of  the 
platinum. 

To  determine  the  constituents  of  the  ore  which  are 
of  no  value,  charge  two  gms.  of  ore  and  ten  gms.  of 
granulated  silver,  well  mixed,  in  a  small  crucible,  the 
sides  of  which  have  been  glazed  with  borax  (melt  some 
borax  in  it),  over  the  mixture  of  borax  and  silver  put 
ten  gms.  borax  glass  and  one  or  two  pieces  of  char- 
coal. Fuse  and  keep  hot  for  some  time ;  cool,  break, 
and  weigh  the  button  of  alloy,  after  carefully  removing 
the  borax  glass.  Subtract  the  weight  of  the  button  from 
the  sum  of  the  weights  of  the  ore  and  silver.  The  dif- 
ference equals  the  impurities  in  the  ore.  The  button 
uan  then  be  treated  as  an  alloy  of  platinum.  (See 
page  121.) 


82  EIEE   ASSAYS. 

ZINC.        Symbol- -Zn. 
SOURCES. — The  principal  ores  of  zinc  are : 

Blende,  sulphide  (ZnS) Pure =67. 7  zino 

Smithsonite,  carbonate  (ZnCO3) "    =52.      " 

Calamine,  silicate  (Zn,Si04+H20) "    =53.8    " 

Willemite,  silicate  (ZnSiG3) "    =58.3    " 

Zincite,  oxide  (ZnO) "    =80.26  " 

The  last  two  occur  associated  with  Franklinite. 

The  first  three  are  found  alone  or  associated  with  the 
ores  of  other  metals  ;  this  being  especially  true  of  the  sul- 
phide which  often  contains  silver  and  is  found  with  galena. 

ASSAY. — The  assay  for  zinc  is  attended  with  considerable 
difficulty,  and  is  not  accurate  save  when  done  in  the 
wet  way  (See  scheme,  p.  122) ;  zinc  being  volatile  and 
easily  oxidized.  The  amount  of  zinc  may  be  estimated 
pretty  closely  by  the  following  method,  when  no  lead  or 
antimony  is  present. 

Weigh  out  10  gms.  of  the  finely  pulverized  ore  and  roast 
it  carefully,  with  the  addition  of  a  little  carbonate  of  am- 
monia to  decompose  any  sulphates  formed.  Weigh  and 
mix  the  residue  with 

Kaolin,  or  china  clay  (dry) 1.0  gm. 

Lime,  "     0.5    " 

and  charge  the  mixture  in  a  charcoal-lined  crucible,  as  in 
the  iron  assay,  'but  not  luting  on  the  cover  tight.  Fuse 
at  as  high  a  temperature  as  possible  for  about  two  and  one- 
half  to  three  hours.  Cool,  and  break  the  crucible  open. 
The  zinc  will  have  been  reduced  and  expelled.  The  residue, 
consisting  of  slag,  and  metallic  globules  if  much  iron  was 
present  in  the  ore,  should  be  weighed  and  powdered.  Sepa- 
rate the  globules  with  the  magnet,  weigh  them,  and 


MEKCUKY.  83 

add  three-sevenths  of  their  weight  to  that  of  the  total  resi- 
due for  the  oxygen  lost  by  reduction.  The  total  weight  thus 
obtained  deducted  from  that  of  the  roasted  ore  and  fluxes 

1  (\  Q 

charged,  and  the  difference  multiplied  by  ^'^  gives  the 
yield  of  metallic  zinc. 

REMARKS. — The  kind  and  amount  of  fluxes  used  depend 
upon  the  character  of  the  gangue  of  the  ore  treated  ;  fusi- 
ble ores  not  requiring  any. 

The  factors  used  to  calculate  the  amount  of  oxygen  and 
the  metallic  zinc  are  deduced  from  the  table  of  atomic 
weights.  (Page  14). 

The  method  given  is  not  applicable  to  ores  where  zinc 
blende  is  associated  with  sulphide  of  lead,  antimony, 
arsenic,  etc.,  and  carries  gold  and  silver.  The  latter  metals 
would  be  reduced  and  go  into  the  buttons  of  iron,  causing 
error  in  the  calculation  of  the  oxygen  to  be  added.  The 
method  for  practical  purposes  may  prove  sufficiently  close, 
but  where  accuracy  is  required  the  wet  method  for  zinc  is 
preferable,  and  is  recommended. 

MERCURY.        Symbol-Hg. 

SOUKCES. — The  principal  ore  of  mercury  is  cinnabar, 
sulphide  (HgS2).  Pure =86. 27.  It  also  occurs  in  the  me- 
tallic state,  alone  and  amalgamated  with  silver,  gold,  etc., 
and  is  sometimes  found  combined  with  chlorine. 

ASSAY.— The  determination  of  mercury  is  made  by  distil- 
lation. 
1.  Ore,  sulphide  or  chloride. 

Charge — Ore,  finely  pulverized 10  gms. 

Black  flux,  substitute 15     " 


MJNIVERSITY 


84  FIEE   ASSAYS. 

This  should  be  mixed  by  rubbing  together  with  water  and 
drying.  The  dried  mixture  being  charged  in  an  iron,  glass 
or  clay  retort,  with  a  bent  neck,  the  end  of  which  is  plunged 
in  a  glass  vessel  to  collect  the  distilled  metal.  It  is  better 
also  to  wrap  the  neck  of  the  retort  with  a  damp  cloth.  The 
retort  may  be  heated  over  a  small  charcoal  furnace,  or  in 
any  way  by  which  the  heat  can  be  applied  slowly,  and  the 
whole  body  of  the  retort  heated,  to  prevent  condensation 
of  the  mercury  on  the  top.  When  after  heating  sometime, 
no  more  mercury  comes  over,  the  end  of  the  neck  should 
be  lifted  out  of  the  water  to  prevent  its  being  drawn 
over  into  the  retort.  The  latter  is  allowed  to  cool  slowly, 
and  all  adhering  particles  of  the  metal  are  brushed  with  a 
feather  into  the  glass  receiver,  where  they  can  be  collected 
by  boiling  the  water  for  a  moment.  The  water  is  then 
decanted,  and  the  mercury  dried  at  the  ordinary  tempera- 
ture or  with  blotting  paper  and  weighed  on  glass.  Some- 
times lime  or  iron  filings  are  used  in  place  of  an  alkaline 
flux  ;  the  object  being,  however,  in  any  case  to  decompose 
the  mercurial  compound,  freeing  that  metal,  the  substance 
used  taking  up  the  sulphur  and  chlorine.  The  determina- 
tions must  be  made  in  duplicate,  and  for  very  poor  ores 
the  pulverized  sample  should  be  first  digested  in  muriatic 
and  nitric  acids  (aqua  regia),  the  solution  filtered  off  and 
evaporated  to  dryness,  and  the  dried  mass  which  will  con- 
tain all  the  mercury  as  chloride,  treated  by  distillation,  as 
described. 

2.     Metallic  mercury  and  amalgams. 

Distill  without  the  addition  of  any  decomposing  agent, 
otherwise  conducting  the  operation  as  above.  The  heat 
used  need  not  be  so  high,  mercury  being  very  volatile.  For 
the  treatment  of  amalgam,  small  iron  crucibles,  with  an 


BISMUTH.  86 

escape  tube  for  the  mercury,  can  be  purchased  of  almost 
any  apparatus  dealer. 

REMAKKS. — For  all  distillations  the  retort  should  be 
tight.  For  this  reason  glass  or  iron  retorts  are  the  best. 
Earthen  retorts  should  be  glazed.  The  operation  should 
be  conducted  under  a  hood,  care  being  taken  not  to  inhale 
any  of  the  fumes. 

The  wet  method  is  preferable  for  mercury  ores. 

See  Mitchell— page  453,  and  Goody  ear's  translation  of 
Bodemann  and  Kerl,  page  207. 


BISMUTH.        Symbol— E\. 

SOUKCES. — This  metal  is  found  principally  in  the  metallic 
state,  but  it  also  occurs  in  combination  with  sulphur, 
oxygen,  and  tellurium,  associated  with  lead  and  silver. 
Bismuth,  like  lead,  possesses  the  property  of  causing 
the  absorption  of  the  metallic  oxides  in  cupellation,  and 
may  be  used  in  place  of  the  latter,  but  is  not  recom- 
mended. 

ASSAY.— In  the  assay  for  bismuth  three  cases  may 
occur. 

a.  The  sample  contains  native  bismuth. 

b.  The  sample  is  composed  of  bismuth  with  other  sub- 
stances, or  bismuth  residue. 

c.  The  sample  is  an  alloy. 

a.  Determine  as  in  the  assay  for  ' '  antimonium  crudum, " 
the  bismuth  being  collected  in  the  same  way. 

b.  Pulverize  finely  and  charge : 


86  FIKE  ASSAYS. 

Ore 10  gms. 

Borax  glass 30     " 

Soda 10     " 

Cyanide  of  Potassium 6     " 

Salt cover 

(See  Mitchell,  page  642). 

Fuse  in  a  moderate  fire  in  the  same  manner  as  for  anti- 
mony. The  resulting  button  must  be  tested  for  other  met- 
als, and  if  any  be  present  treated  as  an  alloy. 

c.     Determine  by  the  wet  assay.     (See  scheme,  page  124). 

REMARKS. — Bismuth  melts  at  268°  C.,  and  is  volatile  at 
a  higher  temperature. 

The  assay  for  bismuth  may  also  be  made  by  fusing  the 
pulverized  and  sintered  ore  (prepared  by  heating  alone  in  a 
closed  crucible)  with  a  known  weight  (five  to  ten  gms. )  of 
fine  silver,  black  flux,  and  three  to  five  gms.  of  iron  wire, 
covering  with  salt.  The  button  can  afterward  be  treated  as 
an  alloy.  Plattner's  Manual  of  Blowpipe  Analysis,  page 
459. 

Cyanide  of  potassium  can  be  used  alone  for  assaying 
bismuth  ore,  as  in  the  assay  for  antimony,  with  good  re- 
sults. 

A  button  of  bismuth  should  not  be  hammered,  as  it  is 
brittle. 


TIN.        Symbol—  Sn. 

SOUECES.— The  most  abundant  ore  is  cassiterite,  binox- 
ide  (SnO3),  =78.67  per  cent,  when  pure.  It  is  found  in  veins 
and  in  the  washings  from  the  same  under  the  name  of  stream 
tin ;  sometimes  it  is  associated  with  tungsten,  tantalum, 


87 

or  molybdenum.     Tin  also  occurs  as  a  sulphide  in  stannite, 
tin  pyrites  SnS2),  and  rarely  in  the  native  state. 


In  the  United  States,  tin  has  been  found  only  in  small 
quantities,  the  ore  not  being  rich  enough  to  pay  for  work- 
ing. 

ASSAY.  —  The  treatment  of  tin  ores  in  the  laboratory  is  a 
matter  of  some  difficulty  for  several  reasons  : 

1st.  The  ore  is  often  associated  with  a  gangue,  the  con- 
stituents of  which  either  form  salts  with  the  oxide  of  tin 
or  alloy  with  the  reduced  metal  from  the  same. 

2d.  The  majority  of  the  basic  fluxes  at  the  disposal  of 
the  assayer,  combine  with  the  tin  and  oxygen  which  may  be 
present,  forming  stannates  which  go  into  the  slag. 

3d.  Acid  fluxes,  especially  silica,  form  compounds  with 
the  oxide  of  tin,  and  carry  it  into  the  slag.  The  influence 
of  silica  can  be  seen  by  the  following  table,  given  by 
Mitchell.  The  last  line  shows  the  yield  of  metal  : 

Ore  ........  10.  00        10.  00        10.  00        10.  QO        10.  00  gms. 

Silica  ......  2.50          6.60        10.00        15.00        30.00     " 

Tin  ........  52^  43%         28%  10  fo          none 

The  fusion  being  made  in  each  case  with  an  equal  quan- 
tity of  black  flux. 

4th.  Binoxide  of  tin  is  extremely  difficult  to  fuse; 
it  is  insoluble  even  in  concentrated  acids,  and  although  it  is 
reducible  by  ignition  with  hydrogen,  charcoal,  etc.,  there  is 
always  danger  of  loss  if  the  temperature  be  too  high,  as  tin 
boils  at  a  white  heat,  air  being  excluded  to  prevent  oxida- 
tion. 

The  various  methods  adopted  for  the  assay  of  tin  may  be 
divided  into  four  classes  : 

a.    For  pure  binoxide  of  tin. 


88  FIKE   ASSAYS. 

5.     For  ore  containing  silica  only. 

c.  For  very  impure  ores,  sulphides,  etc. 

d.  For  alloys  from  the  dry  assay  or  tin  buttons. 

a.  Treatment  of  the  pure  binoxide. 

1.  Charge  ten  gms.  of  ore  finely  pulverized,  into  a  char- 
coal-lined crucible,  lute  the  cover  well  on,  then  heat  for 
twenty-five  minutes,  raising  the  heat  gradually  until  it  is 
almost  white.  Remove  the  crucible  from  the  fire  and  tap 
it  gently.  If  the  tin  be  in  small  globules,  flatten  in  a 
mortar,  and  pass  through  a  fine  sieve  to  separate  from  the 
charcoal.  This  method  gives  good  results  if  the  ore  be  per- 
fectly pure,  but  not  otherwise. 

2.  Ore 10  gms. 

Cyanide  of  Potassium 40     " 

Use  a  small  chalk-lined  crucible,  half  of  the  cyanide  be- 
ing placed  in  the  bottom  of  the  crucible,  and  the  rest 
mixed  with  the  ore.  Cover  with  cyanide  and  then  with 
salt ;  fuse  for  fifteen  minutes  in  a  good  fire,  cool,  break, 
and  weigh.  For  binoxide  and  pure  ores  containing  little 
silica,  this  method  gives  excellent  results. 

Foreign  metals  may  be  removed  before  fusion  by  the 
process  given  on  page  125,  or  the  button  may  be  treated  as 
an  alloy. 

b.  Ores  containing  silica  only. 

1.  Ore 10  gms. 

Fluor  spar  or  cryolite. ..  .10  to  20     " 

Mix  well  and  charge  in  a  charcoal-lined  crucible,  which  is 
first  covered  with  charcoal  and  then  luted  with  clay.  Heat- 
strongly  for  about  one  hour.  Remove  carefully  from  the 
fire  and  tap  gently.  Treat  the  button  as  an  alloy  after- 
wards. 


TIN.  89 

2.  Ore 10  gms. 

Hematite 3  to  8     " 

Cyanide  of  Potassium 40     " 

Mix  and  charge  in  a  charcoal-lined  crucible,  cover  with 
cyanide,  and  then  with  charcoal,  lute  and  heat  strongly 
from  one-half  to  one  hour ;  remove,  tap  carefully,  cool, 
and  break.  If  the  tin  be  in  small  buttons,  collect  by  wash- 
ing with  water  to  separate  the  charcoal,  dry  and  weigh. 
Treat  the  button  as  an  alloy  of  tin  and  iron. 

3.  Ore 10  gms. 

Oxide  of  Copper 10     " 

Black  Flux  Substitute 30     " 

Argol..... 2     " 

Borax  glass 5     " 

Mix,  and  cover  with  salt  and  charcoal,  in  a  chalk-lined 
crucible.  Heat  gradually,  and  finally  to  a  white  heat  for 
one  hour.  Tap,  cool  and  weigh.  Treat  the  button  as  an 
alloy  of  copper  and  tin.  Mitchell,  page  411. 

4.  Ore 10  gms. 

Fluor  spar  10     " 

Powdered  charcoal 2     " 

Salt  and  charcoal cover. 

Mix  well  and  charge  in  an  ordinary  chalk-lined  crucible 
and  use  a  hot  fire.  Treat  the  button  as  an  alloy  if  it  is  not 
soft  and  malleable.  This  method  is  used  in  Cornwall  with 
success. 

c.  Yery  impure  ores,  sulphides,  etc.  Weigh  out  and 
roast  carefully,  first  alone  and  then  with  a  little  charcoal, 
to  remove  arsenic  and  antimony,  adding  finally  carbonate 
of  ammonia  to  decompose  sulphates  ;  then  treat  by  any 


90  FIKE  ASSAYS. 

method  for  ores  containing  silica.  Testing  the  button  foi 
iron,  etc.,  or  after  roasting  separate  all  associated  metals 
by  the  method  on  page  125,  and  then  fuse  for  tin. 

d.  Alloys. — As  tin  fuses  at  228°  C.,  it  may  be  roughly 
separated  from  iron  and  metals  of  a  less  degree  of  fusibil- 
ity, by  simply  heating  the  alloy  so  that  the  melted  tin  can 
drain  off.  The  only  true  way,  however,  is  to  treat  by  the 
wet  method,  page  127. 

REMARKS.  -  -  The  method  by  fusion  with  cryolite  or 
fluorspar  can  be  performed  in  a  small  charcoal-lined  cruci- 
ble, with  two  gms.  of  finely  pulverized  and  well  mixed  ore  ; 
the  crucible  being  luted  and  placed  in  a  cupel  muffle. 

The  time  required  is  about  one-half  hour,  the  muffle  being 
filled  with  charcoal  the  last  fifteen  minutes,  the  door  closed, 
and  as  high  a  heat  obtained  as  possible. 

Assays  of  Durango  tin  ore  containing  silica  by  the  above 
methods,  gave  the  following  average  results  : 

METHOD.  TIN  FOUND. 

a— 2 67.0  to  76.0  per  cent. 

6—1 75.4     "       " 

6—2 74.0     "       " 

b— 3 67.1     "       " 

b— 4 74.0     "       " 

b  — 1,  b — 2,  and  b — 4  seem  to  be  the  only  methods  by  which 
the  tin  is  entirely  reduced.  If  any  foreign  metals  be  present 
in  the  ore,  they  are  likely  to  enter  the  buttons  also,  making 
them  hard. 

COPPER.        Symbol—  Cu. 

SOUKCES. — The  substances  containing  copper  may  be  di 
vided  into  three  classes : 


COPPEE.  91 

1st.     Pure  or  oxidized  ores. 

3d.     Impure  ores,  or  compounds  of  copper  and  otliei 
metals,  with  sulphur,  arsenic,  antimony,  etc. 
3d.     Native  copper  and  alloys. 
The  most  abundant  ores  of  copper  are : 

Native  copper  and  its  silver  alloy Pure =100.    copper. 

Cuprite,  red  oxide  (Cu2O) "   =  88.7       " 

Malachite,  carbonate  (CuCO3  +  CuH,O2).     "    =67.3       " 
A       .,       (  carbonate  and  hydrate )  KK          < 

Azunte,  {  (2CuCo3+CuH2O,).         p" 

Chalcocite,  copper  glance  (Cu9S) "    =  79.8       " 

Chalcopyrite,  copper  pyrites  (CuFeS2) .     "    —  34.6       " 
Erubescite,  purple  copper  (FeCu3S3). . .     "    =55.7       " 

Compounds  with  arsenic,  antimony,  lead,  mercury,  etc., 
the  chloride,  atacamite,  and  the  silicate,  chrysocolla. 

ASSAY. — Copper  can  best  be  determined  in  the  dry  way, 
by  roasting  the  ore  with  carbonate  of  ammonia  and  then 
fusing  with  arsenic  and  slagging  off  the  other  ar- 
senides combined  with  it.     This  method  is  exact 
but  requires  practice.     It  serves  to  determine  be- 
sides the  copper :  lead,  bismuth,  cobalt,  and  nickel. 
The  crucible  used  for  the  fusion  is  shown  in  Fig. 
28.     The  assay  can  be  conducted  in  the  muffle  fur- 
FIG.  28.  nace,  and  involves  the  following  operations  : 
a. — Roasting  with  carbonate  of  ammonia. 
b. — Treatment  of  the  roasted  ore  with  metallic  arsenic. 
c. — Fusion  with  fluxes  to  collect  arsenides  in  a  button, 
and  to  separate  lead  and  bismuth. 

d.— Separation  of  the  arsenide  of  iron,  etc.,  from  the 
arsenides  of  nickel,  cobalt  and  copper. 


9^  FIEE  ASSAYS. 

e. — Removal  of  the  excess  of  arsenic  and  the  separation 
of  arsenide  of  cobalt. 

f. — Fusion  with  gold  and  separation  of  arsenide  of  nickel. 

For  details  of  the  assay  see  method  for  nickel  and  cobalt, 
pages  99  to  102 ;  also  Watts'  Dictionary  of  Chemistry 
Yol.  II. ,  page  63. 

Other  methods  for  assaying  copper  ores  are  in  use,  bul 
are  not  recommended  on  account  of  the  liability  of  loss  of 
copper  in  the  process  of  refining  ;  one  or  two  of  them  are, 
however,  given  below. 

Weigh  out  ten  gms.  of  the  ore  and  roast  it  carefully, 
if  it  contains  sulphur,  arsenic,  etc.,  with  three  times  its 
volume  of  fine  charcoal  or  two  or  three  grammes  of  fine, 
pure  graphite.  If  the  ore  be  very  fusible,  add  five  grammes 
of  powdered  hematite,  mix  the  charge  well  before  roast- 
ing, and  line  the  pan  or  vessel  with  chalk  or  oxide  of 
iron.  Add  carbonate  of  ammonia  toward  the  end  to  decom- 
pose sulphates.  After  roasting  mix  the  ore  with 

Black  Flux  Substitute 20  gms. 

Borax  glass 3     " 

Hematite  (peroxide  of  iron)  10  to  20     " 

Cover  with  a  mixture  of  ten  gms.  black  flux  substitue  and 
three  gms.  charcoal,  then  with  salt.  Fuse  in  an  ordinary 
chalk-lined  crucible  for  twenty  minutes.  When  perfectly 
fused,  pour  carefully  into  a  mould. 

The  resulting  copper  button  must  be  refined  by  fusing  it 
as  quickly  as  possible  in  a  shallow  dish  in  the  cupel  muffle, 
with  an  equal  weight  of  borax  or  less,  and  a  little  pure  lead  ; 
one  to  two  grammes  will  generally  be  sufficient,  and  if  the 
ore  contains  lead,  its  addition  is  unnecessary.  When  the 
copper  is  nearly  refined  it  brightens  somewhat  like  silver, 
only  less  distinctly,  showing  a  peculiar  green  color.  If 


COPPER.  93 

the  button  is  small,  the  assay  is  considered  finished  when 
it  no  longer  fumes. 

Instead  of  the  above,  the  following  charge  may  be  used 
in  fusing. 

Ore 10  gms. 

Black  Flux  Substitute 25     " 

Argol 2     " 

Borax  Glass 5     " 

Litharge 6     " 

Mix  well  and  cover  with  salt  and  charcoal.  Then  refine 
as  described.  The  action  in  the  crucible  is  reducing.  An 
alloy  of  copper  and  other  metals,  if  present,  being  formed 
which  must  be  refined. 

REMARKS. — A  good  refining  flux  is 

Nitre 3    pts. 

Argol., 2J-     " 

Salt 1       " 

Fuse  together,  pulverize,  sift  through  a  thirty-mesh 
sieve,  and  test  its  action  on  an  alloy  of  copper  before 
using. 

Iron  prevents  loss  of  copper  in  the  slag,  which  is  always 
the  case  when  the  latter  has  a  red  color,  due  to  the  sub- 
oxide  of  copper.  If  the  button  from  the  crucible  is  small 
the  best  way  is  to  refine  it  before  the  blowpipe  on  charcoal, 
with  a  little  boracic  acid,  blowing  on  the  slag  only,  after 
the  assay  is  once  fused. 

If  many  ores  are  to  be  tested,  the  wet  method  will  be 
found  the  most  convenient  and  accurate,  especially  if  the 
ores  contain  silver  and  gold,  which,  as  they  go  with  the 
copper,  would  materially  affect  the  results  by  tending  to 
increase  the  percentage. 


94  FIKE  ASSAYS. 

IRON.        Symbol— Fe. 

SOUECES. — The  following  is  a  list  of  the  principal  ores  of 
iron. 

Magnetic  iron  ore,  oxide  (Fe3O4) Pure=72.41  iron. 

Red  hematite    or    specular    iron,    oxide 

(Fe2O3) "    =70.00    " 

Brown  hematite  or  limonite,  oxide  (2Fe2O3. 

3H80) "    =59.92    " 

Spathic  iron  ore,  carbonate  (FeC03) "    =48.22    " 

Ilmenite,  titaniferous  ore  (FeTi03  + 

nFe2O3) "    =36.82    " 

Franklinite  (Fe,  Zn,  Mn)(Fe.2Mn2)O4 "    =  48. 00    " 

Chromite  (FeCr2O4).     Also  Sulphides,  as  Pyrite,  Pyrrho- 

tite,  etc. 

ASSAY. — It  is  required  in  the  assay  for  iron  not  only  to 
reduce  the  oxide  to  cast-iron,  collect  the  latter  in  a  button, 
and  to  form  a  fusible  slag  that  will  not  retain  any  of  the 
iron  in  combination  or  in  pellets,  but  also  to  use  such 
fluxes  and  adjust  them,  so  the  results  will  indicate  the 
character  of  the  ore,  quality  of  iron  it  will  yield  on  smelt- 
ing, etc.  The  oxide  is  reduced  by  carbon,  and  we  employ 
for  this  purpose  crucibles  lined  with,  brasque,  which  is  a 
composition  of  four  parts  finely  pulverized  charcoal  to  one 
of  molasses.  (To  prepare  this,  see  page  28.) 

The  lining  serves  as  a  support  for  the  crucible,  which 
under  the  high  heat,  is  apt  to  soften. 

In  making  up  the  charge  we  may  have,  (1)  Ores 
of  unknown  composition,  and  (2)  Ores  previously  an- 
alyzed. The  assay  in  both  cases  gives  a  clue  to  the  na- 
ture of  the  slag,  the  iron  that  may  be  obtained  from 
the  ore,  and  the  character  and  proportion  of  the  fluxes  to 


IKON.  95 

be  added  in  the  blast  furnace.  In  the  first  case  we  obtain 
the  additional  information  of  the  approximate  percentage 
of  iron. 

1.  Ores  of  unknown  composition. 

In  the  assay  of  an  ore  the  composition  of  which  is  un- 
known, we  make  several  preliminary  assays,  and  if  satis- 
factory results  are  obtained  we  make  another  assay  with  a 
charge  modified  according  to  the  indications  of  the  best  pre- 
liminary assay. 

Preliminary  assay  charges  : 

1.  2.  3.  4. 

Silica 2.5  1.          4.0          2.5  to  0.  gms. 

Lime 2.5  4.  1.0          2.5  to  3.     " 

Ore 10.0          10.         10.0        10.0  " 

1  is  employed  for  the  purer  ores  containing  very  little 
gangue ;  2,  for  ores  containing  silica ;  3,  for  ores  contain- 
ing the  carbonates  of  lime,  magnesia,  protoxide  of  man- 
ganese, etc.,  calcareous  hematites  and  spathic  iron ;  4,  for 
ores  containing  silica  and  alumina,  clay  iron  stones,  black 
band,  etc. 

The  principle  involved  is  that  of  furnishing  a  base  for  an 
acid,  and  vice  versa.  The  charge,  therefore,  depends  upon 
the  acid  or  basic  nature  of  the  gangue  of  the  ore. 

Ores  containing  titanium  require  the  addition  of  fluor- 
spar to  the  charge  in  quantity  varying  from  0.5  to  10  gms* 

2.  Ores  previously  analyzed. 

Good  results  are  obtained  from  a  charge  proportioned  to 
yield  a  slag  corresponding  to  a  blast  furnace  cinder,  hav- 
ing the  composition  RSO3.  SiO3  +  2(3RO.  SiO3),  as  given  by 
Percy. 

E,2O3  represents  alumina,  and  EO,  lime,  magnesia,  and 
other  bases.  Its  approximate  percentage  composition  is  as 
follows : 


96  FIKE   ASSAYS. 

Silica 38.  j  /  2J  parts. 

R,O3  (alumina) 15.  >  or  about  <l         " 

RO  (lime, magnesia, etc.) 47.  )  (3         " 

The  method  of  charging  can  best  be  shown  by  example 

The  Ore  p      -,     ,      10  gms.  of  ore      Slag  Difference 

contains.  contains,      required.  to  be  added. 

Silica. 1.65          0.165          2.50          2.335  gms. 

Alumina 1.94          0.194          1.00          0.806     " 

Lime,  magnesia, etc. 4. 51          0.451          3.00          2.549     " 

The  alumina  is  added  in  the  form  of  kaolin  or  fire-clay, 
which  contains  nearly  equal  parts  of  alumina  and  silica. 
Allow  in  adding  silica  for  that  introduced  in  the  kaolin. 

Sometimes  the  ore  contains  more  than  one  of  the  ingre- 
dients of  the  slag,  or  the  silica  introduced  with  the  kaolin 
may,  when  added  to  that  already  present,  increase  the 
quantity  beyond  what  is  required.  In  either  case  make  up 
a  new  slag  with  the  excess,  retaining  the  same  proportion 
between  the  silica,  alumina  and  lime,  viz  :  silica,  2| ;  alum- 
ina, 1 ;  lime,  3.  For  example,  see  Part  IV.,  page  168. 

The  charge  should  be  thoroughly  mixed,  placed  in  the 
crucible,  the  conical  cavity  closed  with  a  piece  of  charcoal, 
and  the  whole  top  of  the  crucible  covered  with  a  luting  of 
fire-clay.  The  latter  is  mixed  with  one-fourth  to  one-third 
part  of  fine  sand  and  made  plastic  with  borax  water. 

Four  crucibles  are  introd.uced  in  the  furnace  luted  to  a 
fire-brick,  and  a  low  fire  kindled  around  them.  The  fuel  is 
added  gradually  until  it  is  above  the  tops  of  the  crucibles  : 
the  fire  is  maintained  at  its  maximum  temperature  for  twe 
and  one-half  to  three  and  one-half  hours.  Ores  containing 
much  titanium  require  four  hours,  while  carbonates  con- 
taining manganese,  fuse  well  in  two  and  one-half  hours,  or 
even  less  time.  When  the  fire  has  burned  out  the  bricks 
and  crucibles  are  removed  in  one  mass,  the  crucibles  de- 
tached and  their  exteriors  broken  witli  a  hammer;  on 


97 

inverting  and  tapping  the  charcoal  lining  the  slag  and  but- 
ton of  cast-iron  will  fall  into  the  hand.  If  they  adhere  to- 
gether, a  slight  tap  serves  to  separate  them. 

Before  separation  they  should  be  carefully  cleansed  and 
weighed,  the  slag  may  then  be  broken,  and  any  particles  of 
Iron  separated  with  a  magnet,  and  weighed  with  the  button. 

Titanium  and  manganese  enter  the  slag  almost  completely. 
Duplicate  assays  should  not  differ  more  than  0.3  to  0.4  of 
one  per  cent.  The  slag  ought  to  be  well  fused  and  free 
from  iron.  A  good  button  is  well  formed  and  easily  de- 
tached from  the  slag. 

If  the  metal  be  of  good  quality  the  button  will  flatten 
slightly  before  breaking.  It  ought  to  be  gray  or  grayish 
white,  and  the  grain  fine. 

A  button  of  bad  iron  breaks  readily  without  changing 
form. 

Transparent  slags  of  a  greenish  tint  indicate  excess  of  silica. 
A  rough,  stony  slag,  or  one  crystalline  in  structure  and  dull 
in  lustre  indicates  an  excess  of  bases.  If  the  product  is 
only  fritted  and  contains  the  reduced  iron  interspersed  as  a 
fine  gray  powder,  silica  and  alumina  are  deficient  in  the  flux, 
lime  and  magnesia  being  in  excess. 

Magnesia  is  one  of  the  most  refractory  bases  found  in 
iron  ores,  and  when  present  in  quantity  requires  an  addi- 
tion of  both  silica  and  lime. 

Manganese  gives  an  amethystine  tint  to  the  slag,  or  if  in 
excess  a  yellow,  green  or  brown  color. 

Titanium  produces  a  resinous,  black,  scoriaceous  slag, 
curiously  wrinkled  on  the  outside,  and  covered  with  me- 
tallic pellicles  of  nitro-cyanide  of  titanium  with  its  char- 
acteristic copper  color ;  sometimes  the  slag  is  vitreous  and 
of  a  bluish  tint. 


98  FIRE  ASSAYS. 

Chromium  gives  a  dark  resinous  slag  surrounded  with  a 
thin  metallic  coating. 

Phosphorus  gives  a  hard,  brittle,  white  metal,  called  cold 
short  iron. 

Sulphur  a  strong,  reticulated,  mottled  structure,  and  red 
short  iron. 

Manganese,  a  button  smooth  on  the  exterior,  hard  and 
non-graphitic  ;  it  presents  a  white  crystalline  fracture. 

Titanium — The  button  is  smooth  on  the  outside,  has  a 
deep  gray  fracture,  dull  and  crystalline,  and  adheres  strong- 
ly to  the  slag.  The  button  is  sometimes  covered  with  the 
nitro-cyanide  of  titanium  with  its  characteristic  copper 
color. 

Chromium — The  button  is  smooth,  well  fused,  with  a  bril- 
liant crystalline  fracture,  and  tin-white  color  ;  at  other  times 
it  is  white  and  only  half  fused,  or  it  may  even  form  a 
spongy  mass  of  a  clear  gray  color,  according  to  the  quan- 
tity of  chromium  contained  in  the  iron. 

REMARKS. — A  number  of  type  ores  gave  on  assay  : 

Ore.  Iron  by  Analysis.  By  Fire  Assay. 

Magnetite 68. 35  per  cent.        69. 6    71 . 2    71 . 3  per  cent. 

Hematite 44.50       "  44.6    46.0    48.6       " 

Limonite 44.20       "  44.3    44.6    45.2       " 

Assays  of  magnetite  containing  titanic  acid  gave  72.5  and 
73.  per  cent. 

Another  magnetite 64.0        64.5  per  cent. 

Hematite 39.0        38.5       " 

Limonite 34.0        34.0       " 

Other  slags  besides  the  one  given  might  be  used,  as 
Bodemann's,  which  is  silica  56,  lime  30,  alumina  14  per 
cent. ,  an  addition  of  borax  and  fluor  spar  makes  this  slag 
more  fluid. 


NICKEL   AND   COBALT.  99 

NICKEL  AND  COBALT.          Symbols— NL  and  Co. 

SOURCES. — These  two  metals  are  generally  found  associ- 
ated, and  their  treatment  will  be  described  under  the  same 
head. 

The  principal  ores  of  nickel  are  niccolite,  copper  nickel 
(MAs),  pure =43  per  cent,  nickel.  Millerite,  sulphide 
(NiS),  pure =64. 4  per  cent,  nickel. 

The  principal  ores  of  cobalt  are  smaltite,  tin- white  co- 
balt (Co,Fe,M)As2,  pure =9  to  33  per  cent,  cobalt.  Co- 
baltite  (CoS2  +  CoAs2),  pure =35. 5  per  cent,  cobalt. 

Both  nickel  and  cobalt  occur  in  many  other  minerals, 
chiefly  in  combination  with  sulphur  or  arsenic,  and  associ- 
ated with  iron,  copper,  lead,  etc. 

We  have  also  an  artificial  product  called  "  spiess,"  which 
is  an  arsenide  of  cobalt,  nickel,  and  iron,  obtained  in  the 
smelting  of  ores  which  contain  nickel  and  cobalt,  and  in  the 
manufacture  of  smalt  (cobalt  glass). 

ASSAY. — Cobalt  and  nickel  being  difficult  to  fuse  they  are 
determined  in  combination  with  arsenic.  Weigh  out  from 
two  to  five  grammes  according  to  the  purity  of  the  ore, 
roast  thoroughly  in  the  muffle,  using  a  clay  roasting  dish, 
and  mixing  with  six  to  ten  grammes  of  fine  charcoal  toward 
the  last  of  the  operation.  When  the  sample  has  ceased  to 
evolve  fumes,  mix  thoroughly  with  one  to  five  gms.  car- 
bonate of  ammonia,  and  heat.  The  resulting  oxides  are 
then  converted  into  arsenides  by  moistening  and  rubbing 
in  a  mortar  with  one  to  five  gms.  metallic  arsenic,  and 
placing  the  mixture  in  a  small  clay  crucible  (Fig.  7),  which 
will  stand  in  the  muffle,  and  heating.  Keep  at  a  dull  red 
until  the  fumes  of  arsenic  have  ceased  ;  when  the  cru- 
cible is  removed,  and  about  thirty  gms.  of  black  flux, 


100  FIKE  ASSAYS. 

or  its  substitute,  and  one  or  two  gms.  of  borax  glass  is 
added,  with  a  covering  of  salt.  Do  not  mix  the  flux, 
but  place  it  over  the  mass  in  the  crucible ;  after  which 
heat  in  a  good  fire,  raising  the  temperature  gradually, 
until  the  contents  of  the  crucible  are  in  a  quiet  state 
of  fusion.  Make  the  heat  strong  toward  the  end  of 
the  operation,  but  be  careful  not  to  let  the  charge  boil 
over.  Cool  and  break  the  crucible,  remove  and  weigh 
the  button  (a)  of  arsenides  of  cobalt,  nickel,  iron,  cop- 
per, etc.  The  rest  of  the  process  consists  in  scori- 
fying the  button,  first,  to  remove  the  iron,  and  after- 
wards to  separate  the  nickel  and  cobalt.  This  can  be 
done  in  a  shallow  dish,  or  on  a  piece  of  clay  crucible 
about  two  inches  long  by  one  inch  wide  and  slightly 
concave,  in  the  cupel  muffle,  which  should  be  pretty  hot 
and  contain  a  piece  of  glowing  charcoal  in  front.  Place 
on  the  dish  the  button  of  arsenides  from  the  fusion  and 
cover  it  with  borax  glass.  Introduce  it  into  the  muffle  and 
close  the  latter  until  the  button  and  borax  are  fused,  then 
allow  air  to  enter.  The  arsenide  of  iron  will  oxidize  first 
and  go  into  the  slag,  and  the  surface  of  the  button  will  be- 
come bright,  when  the  dish  should  be  removed  immediately, 
placed  upon  the  surface  of  a  basin  of  water  until  the 
button  solidifies,  and  then  immersed ;  or  the  button 
can  be  removed  while  the  slag  is  fluid  with  a  pair  of 
pincers.  If  the  slag  shows  a  slight  blue  color  the  iron  is 
entirely  removed,  and  the  button  may  be  cleaned  and 
weighed  (£). 

If  the  desired  purity  from  iron  is  not  obtained  by  one 
scorification  repeat  the  operation,  weighing  the  button  each 
time.  Should  the  button  become  bright  immediately,  show- 
ing that  little  or  no  iron  was  contained,  take  the  previous 


KICKEL   AXD   COBALT.  101 

weight.  The  button  will  consist  of  arsenide  of  nickel,  co- 
balt and  copper  (M4As2.  Co4As2.  CnfiAs2). 

Next  slag  off  the  cobalt  in  the  same  manner  as  the  iron. 
This  operation  must  be  continued  until  an  apple-green 
film  forms,  which  will  float  about  on  the  surface  of  the 
button,  best  seen  by  partially  cooling  the  assay.  Weigh 
the  button  (c). 

If  copper  is  present  add  100  to  500  milligrammes  of  gold 
(weighed),  and  then  proceed  to  slag  off  the  nickel  with  the 
addition  of  a  little  salt  of  phosphorus,  conducting  the  opera- 
tion as  before,  until  the  button  shows  the  bluish-green 
color  peculiar  to  gold  and  copper  when  melted.  Weigh  the 
alloy  of  copper  and  gold  (d). 

To  determine  the  weight  of  copper,  subtract  the  weight 
of  gold  added,  from  the  button  (d).  The  difference  will 
be  the  metallic  copper.  To  determine  the  weight  of  nickel, 

-1  AA 

multiply  the  weight  of  the  copper  by  ,  this  will  give 

the  arsenide  of  copper  (Cu6As2),  which,  subtracted  from  the 

weight  (c),  will  give  the  arsenide  of  nickel.     This  multipled 

60  73 
by  -     rr=the  nickel.   To  determine  the  cobalt  subtract  the 

61  54 
weight  (c)  from  (b)  and  multiply  by      '      . 

1U(J 

The  results  thus  obtained  divided  by  the  weight  of  ore 
taken  for  assay  and  multiplied  by  100  gives  the  percentage 
in  each  case. 

REMARKS. —  Results  compare  well  with  the  battery 
process.  The  following  is  the  composition  of  the  arse- 
nides : 

Cu6As.2  Ni4Ass  Co4As9 

As=28.31  perct.     As=39.27    per  ct.      As =38. 46  per  ct. 

Cn=71.69         "        JSTi=60.73         "          Co=61.54       " 

When  the  ore  treated  contains  bismuth  and  lead  in  any 


102  FIEE   ASSAYS. 

quantity  these  metals  can  be  separated  during  the  fusion 
with  black  flux  by  adding  one  gin.  of  iron  wire,  and  one  to 
three  gms.  of  pure  silver,  accurately  weighed.  After  fusion 
the  lead  and  bismuth  will  be  found  alloyed  with  the  silver, 
and  can  be  detached  without  trouble  from  the  arsenides. 
By  deducting  the  silver,  the  lead  and  bismuth  may  be  de- 
termined. When  the  substance  treated  is  poor  in  nickel 
and  cobalt,  it  is  well  to  add  some  collecting  agent  in  the 
fusion.  Arsenide  of  iron  is  the  best  for  this  purpose  ;  it 
may  be  prepared  by  fusing  iron  filings  with  metallic  arsenic 
in  a  crucible  and  powdering. 


CARBON.         Symbol— C. 

SOURCES. — Carbon  occurs  in  a  vast  number  of  compounds 
forming  with  hydrogen,  oxygen,  and  nitrogen,  an  immense 
series  of  organic  substances ;  but  we  will  only  give  the 
method  for  the  assay  of  coals,  although  the  following  list 
may  be  of  interest  to  the  assayer  : 

Diamond,  pure  carbon crystallized. 

Graphite,  nearly  pure 95 — 100  per  cent. 

Anthracite 90—  95       " 

Bituminous  coal variable. 

Peat  and  lignite about  60  per  cent. 

Charcoal variable. 

ASSAY. — The  assay  of  a  specimen  of  coal  varies  with  the 
purpose  for  which  the  coal  is  to  be  employed.  The  most 
general  tests  are :  Determination  of  moisture,  specific 
gravity,  heating  power,  volatile  products,  coke,  ash,  and  in 
some  cases,  sulphur  and  phosphorus. 

The  moisture,  volatile  products,  coke,  and  ash  may  be 


CARBON.  103 

determined  by  the  scheme  given  below.  The  specific 
gravity  by  formulae,  pages  150-152.  Knowing  the  elemen- 
tary constitution  of  the  fuel,  the  heating  power  may  be 
tested  by  determining  the  amount  of  oxygen  required  to 
burn  it. 

Charge — 1  gm.  of  powdered  coal  and  50  gms.  of  litharge, 
well  mixed,  in  a  crucible,  and  cover  with  20  gms.  of  lith- 
arge. Heat  gradually  until  fusion  is  complete.  The  time  re- 
quired will  be  about  ten  minutes.  Cool  and  break  the  cru- 
cible, then  weigh  the  button  of  lead.  Pure  carbon  should 
reduce  thirty-four  times  its  own  weight  of  lead.  Hydrogen 
103.7  times  its  weight.  Instead  of  litharge,  white  lead 
may  be  used,  the  proportion  being  one  gm.  of  coal  to 
seventy  gms.  of  white  lead,  and  thirty  gms.  of  the  same 
for  a  cover.  If  the  white  lead  be  pure  it  is  better  than 
litharge. 

To  calculate  the  results,  compare  with  the  amount  of 
oxygen  consumed  in  burning  a  fuel  whose  calorific  power  is 
known.  One  part  of  pure  carbon  can  raise  the  temperature 

of  8080  parts  of  water  1°.  Consequently  the  value  of  the  fuel 

80SO 
in  units  of  heat  may  be  estimated  by  multiplying  -~j-    by 

the  weight  of  the  lead  button  obtained  in  the  assay.  When 
much  hydrogen  is  present  in  the  fuel  the  method  is  not  so 
accurate.  The  specific  calorific  effect  of  a  fuel  may  be  esti- 
mated by  multiplying  the  absolute  effect  by  the  specific 
gravity  of  the  fuel. 

To  determine  moisture,  volatile  and  combustible  matter, 
fixed  carbon  (coke),  asli,  and  sulphur. 

a.  Determination  of  moisture.  Pulverize  the  coal  finely, 
heat  one  to  two  gms.  in  a  covered  platinum  or  porcelain  cru- 
cible fifteen  minutes,  in  an  air  bath  at  212°  to  220°  F.  Cool 


104  FIRE   ASSAYS. 

and  weigh,  repeat  until  weight  is  constant,  or  begins  to  rise. 
Loss = moisture. 

b.  Determination  of  volatile  and  combustible  matter. 
Heat  the  same  crucible  with  contents,  to  bright  redness 
over  a  Bunsen  burner  or  alcohol  lamp,   exactly  three  and 
one-half  minutes,  and  then  three  and  one-half  minutes  over 
a  blast  lamp.     Cool  and  weigh.     Loss = volatile  and  com- 
bustible matter.     This  also  includes  one-half  the  sulphur 
from  any  sulphide  of  iron  contained  in  the  coal. 

c.  Fixed  carbon.     Heat  over  the  burner  until  the  ash 
is  white  and  constant  in  weight.     Loss = fixed  carbon  and 
one-half  the  sulphur  from  the  sulphide  of  iron. 

The  sulphur  must  be  determined  by  the  wet  method, 
page  135.  For  the  determination  of  phosphorus,  the  reader 
must  refer  to  some  larger  work,  as  Fresenius  on  Quanti- 
tative Analysis. 

REMARKS. — In  reporting  an  analysis  of  a  coal,  deduct 
the  sulphur  as  mentioned,  and  enter  it  as  a  separate  item 
in  the  analysis,  so  that  it  will  add  up  correctly.  Any  phos- 
phorus present  will  be  contained  in  the  ash  ;  if  determined, 
allow  for  it. 

To  determine  the  actual  volatile  matter  for  gas  making 
purposes,  a  very  rough  but  simple  plan  is  to  heat  a  small 
sample  in  an  ordinary  clay  pipe,  luting  the  top  of  the 
bowl,  so  that  the  volatile  products  will  pass  out  through  the 
stem,  at  the  end  of  which  the  gas  can  be  lighted. 

Analysis  of  two  samples  of  different  semi-bituminous 
coal  gave  the  following  results  in  one  hundred  parts  : 

Moisture 3.310          0.965 

Volatile  combustible  matter  + ±  sulphur ...  27. 300        30.  Ill 

Fixed  carbon  +  J  sulphur 61.965        61.033 

A.sh,  including  phosphorus 7.425          7.829 

Sulphur 3.863          1.347 


CAKBON.  105 


27.300  minus  8tbuo,  and  30.111  minus  x'^t/,  gives  the  cor- 
rect amount  of  volatile  matter. 

61.965  minus  — |^,  and  61.033  minus  ^-—,  gives  the 
rect  amount  of  fixed  carbon. 


PART  III. 

WET  ASSAYS  OR  ANALYSES. 


SILVER  BULLION.  109 

SILVER  BULLION. 

This  process  embraces  two  steps  : 

a.     Preliminary  assay.     5.     Assay  proper. 

The  latter  requires  for  its  conduct  three  solutions,  called 
normal  salt,  decime  salt,  and  decime  silver. 

The  normal  salt  is  a  solution  of  salt,  100  c.c.  of  which  will 
precipitate  exactly  1  gm.  of  pure  silver. 

The  decime  salt  is  a  solution  one-tenth  the  -strength  of 
of  the  normal.  One  c.c.  will  precipitate  one  milligramme 
of  silver ;  it  is  made  by  diluting  one  part  of  the  normal 
solution  with  nine  parts  of  pure  water. 

The  decime  silver  is  a  solution  of  one  gm.  of  pure  silver 
in  nitric  acid,  diluted  to  a  litre.  One  c.c.  of  this  solution 
will  contain  one  milligramme  of  pure  silver.  One  c.c.  de- 
cime silver  is,  therefore,  equivalent  to  one  c.c.  decime  salt. 

PREPARATION  OF  THE  NORMAL  SALT  SOLUTION. — A  large 
quantity  of  the  solution  is  prepared  and  preserved  in  a 
common  glass  carboy,  which  has  affixed  to  it  a  paper  scale 
carefully  graduated,  indicating  its  contents  at  any  time. 
It  is  made  by  diluting  2.07  parts  of  a  saturated  solu- 
tion of  salt  with  97.93  parts  of  pure  water,  or  until  each 
100  c.c.  of  the  resulting  solution  contains  just  0.54167  of  a 
gramme  of  salt,  which  is  the  amount  necessary  to  precipi- 
tate one  gm.  of  pure  silver.  The  amount  of  concentrated 
solution  required  for  100  c.c.  of  the  normal,  depends  upon 
its  strength,  which  can  be  determined  by  evaporating  a 
measured  portion  to  dryness,  and  weighing  the  residue. 
The  normal  solution  must  be  well  mixed  and  the  tubes  and 
pipette  washed  out  by  allowing  some  to  run  through  them. 
The  solution  must  then  be  accurately  standardized.  For 
this  purpose  three  or  four  solutions  of  silver  in  nitric 


WET  ASSAYS. 

acid  are  prepared,  called  check  assays,  each  containing  one 
gm.  pure  silver.  The  solutions  are  made  with  strong  acid 
in  glass  stoppered  bottles  of  8  ozs.  or  250  c.c.  capacity. 
Prepare  also  a  temporary  decime  salt  solution  by  diluting 
25  c.c.  of  the  approximate  normal  with  225  c.c.  of  water. 
Run  into  one  of  the  check  assays  100  c.c.  of  the  normal, 
agitate  and  allow  the  precipitated  chloride  of  silver  to  set- 
tle. Repeat  the  agitation  if  necessary  until  the  solution 
settles  clear  and  bright,  add  now  one  c.c.  of  the  decime  salt 
solution.  Agitate  as  before,  add  again  one  c.c.  of  the  decime 
salt,  and  repeat  until  a  precipitate  fails  to  appear.  Sup- 
pose we  have  added  altogether  14  c.c.,  the  last  produced  no 
precipitate  and  is  not  counted.  Thus  101. 3  parts  of  the 
normal  solution  are  necessary  to  precipitate  one  gramme  of 
silver,  while  only  100  should  be  required.  The  normal 
is  too  weak,  and  the  quantity  of  salt  solution  to  be  added 
may  be  found  by  dividing  the  number  of  c.c.  of  con- 
centrated salt  solution  used  to  make  the  normal  by  100 
— 1.3  or  98.7,  and  multiplying  by  1.3,  the  number  of  decime 
added  after  correction.  The  solution  is  again  tested,  a  new 
decime  salt  made,  and  so  on.  If  the  normal  be  too  strong, 
calculate  from  the  silver  precipitate  the  excess  of  salt  in  the 
whole  solution,  and  water  in  the  ratio  prescribed  to  dissolve 
it.  Let  a = excess  of  silver  precipitated  over  1  gm.,  hence 
1 :  a  :  :  0.54167  :  #=salt  in  excess  in  100  c.c.  of  the  normal. 
®  X  lOO^number  c.c.  of  water  to  add  per  100  c.c.  oi 
solution  remaining  in  carboy. 

a.  PRELIMINAEY  ASSAY. — This  is  rendered  necessary 
by  the  fact  of  our  employing  a  constant  volume  of  normal 
salt  solution  corresponding  to  one  gm.  of  pure  silver. 

Weigh  out  500  mgs.  of  the  alloy,  and  wrap  it  in  pure 
lead  foil,  which  should  be  kept  in  small  sheets  about  two 


SILYEE  BULLION.  Ill 

17 

inches  square,  weighing  r       oz.  ;  or  5.287  gms.  each,  and 


cupel.  Suppose  we  obtain  a  button  of  silver  weighing 
0.43475  gms.,  then,  500  :  1000  ::  0.43475  :  #=869.5,  approx- 
imate fineness.  Corrections  for  loss  of  silver  by  cupellation 
can  then  be  made  by  the  following  table.  They  are  given 
in  thousandths,  and  must  be  added  to  the  standard  : 

STANDARD.   CORRECTION.    STANDARD.   CORRECTION.    STANDARD.   CORRECTION. 


998.97 

1.03 

670.27 

4.73 

346.73 

3.27 

973.24 

1.76 

645.29 

4.71 

322.06 

2.94 

947.50 

2.50 

620.30 

4.70 

297.40 

2.60 

921.75 

3.25 

595.32 

4.68 

272.42 

2.58 

896.00 

4.00 

570.32 

4.68 

247.44 

2.56 

870.93 

4.07 

545.32 

4.68 

222.45 

2.55 

845.85 

4.13 

520.32 

4.68 

197.47 

2.55 

820.78 

4.22 

495.32 

4.68 

173.88 

2.12 

795.70 

4.30 

470.50 

4.50 

148.30 

1.70 

770.59 

4.41 

445.69 

4.31 

123.71 

1.29 

745.38 

4.52 

420.87 

4.13 

99.12 

0.88 

720.36 

4.64 

396.05 

3.95 

74.34 

0.66 

695.25 

4.75 

371.39 

3.61 

49.56 

0.44 

Example:  The  number  in  the  column  of  standards  near- 
ejst  to  869.5  is  870.93  ;  the  corresponding  correction  is  4.07  ; 
adding  this  to  869.5,  we  obtain  873.57  for  the  true  approx- 
imate fineness. 

b.  ASSAY  PEOPEE. — Take  such  a  weight  of  alloy  as  will 
contain  one  gm.  of  pure  silver.  This  is  found  from  the 
approximate  fineness,  by  the  following  proportion  :  873.57 
is  to  1000  as  1  is  to  x = 1 . 145  gms.  Place  this  in  a  glass-stop- 
pered bottle  of  about  8  oz.  capacity,  and  dissolve  in  10  c.c. 
nitric  acid.  Heat  gently  on  the  sand  bath  to  facilitate  so- 
lution, and  cool.  Add  100  c.c.  of  the  normal  solution,  and 
proceed  in  the  same  way  as  in  standardizing  the  normal 
until  the  decline  salt  fails  to  give  a  precipitate.  Suppose 
we  have  added  6  c.  c.  of  the  decime  salt ;  the  last  gave  no 


112 


WET   ASSAYS. 


X 


precipitate  ;  so  that  we  required  more  than  4  and  less  than 
5,  or  4.5  c.c.  If  greater  accuracy  be  necessary,  check  with 
the  decime  silver  solution.  We  have  used  100.45  of  salt 
solution— 1.0045  gins,  of  silver.  The  fineness  is  given  by 
the  following  proportion  :  1 . 145  is  to  1 . 0045  as  1000  is  to  x = 
the  fineness. 

APPARATUS  EMPLOYED. — (Fig.  29). 
The   carboy   should   hold    about  60 
litres  or  15  to  16  gallons,  and  have  a 
paper  scale  affixed  to  it,  graduated 
by  adding  successively  a  known  num- 
ber of  litres  of  water  until  the  car- 
boy is  filled,  and  marking  after  each 
addition  the  height  of  the  liquid.     B 
and  V  are  parts  of  a  valve.     B  is  the 
cover  of  glass    through    which    the 
i /tubes  pass,  fitted  by  a  cork.     V  is  a 
neck  of  sheet-iron  four  inches  deep. 
The  valve  is  closed  with  mer- 
cury to  about  one-third  of  it$ 
height.     An  enlarged  section 
of  the  valve  is  shown  at  Y. 
The  tube  T  and  the    siphon 
S  reach  nearly  to  the  bottom 
of  the  carboy.      The  former 
admits  air,  and  as  none  can 
pass  out  evaporation  is  pre- 
vented. The  siphon  is  jointed 
with  rubber  at  a,  and  has  a  stopcock  at  b. 
It  is  furnished  at  the  lower  end  with  a 
piece  of  rubber  tubing  for  connecting  with 
FIG.  29.          the  lower  part  of  the  pipette  P  ;  which  is 


SILVER  BULLION.  113 

supported  by  brackets  c  c,  affixed  to  the  wall  of  the  room 
or  an  upright  standard.  The  upper  extremity  of  the  pipette 
P,  passes  through  a  vessel  d,  designed  to  catch  the  liquid 
running  over.  The  method  of  using  the  apparatus  is  to  at- 
tach the  tube  to  the  pipette,  open  the  pinch-cock  e,  allow 
the  normal  solution  to  flow  upwards  into  the  pipette, 
until  the  latter  overflows.  Stop  the  flow,  close  with  the 
finger,  remove  the  rubber  tube  and  wipe  off  any  of  the  so- 
lution adhering  to  the  outside  of  the  pipette,  which  is 
now  ready  on  removing  the  finger,  to  deliver  100  c.  c.  of  the 

normal  solution.  Fig. 
30  shows  a  very  con- 
venient apparatus  for 
holding  the  glass  bot- 
tle which  receives  the 
liquid  from  the  pipette 
and  catching  the  drip- 
pings. C  is  a  cylinder  of 
FIG.  30.  tin-p]ate  to  receive  the 

assay  bottle.  E  is  a  sponge  enveloped  in  linen,  forced  into 
a  tube  of  tin-plate,  terminated  above  by  a  cup  and  open 
below,  so  that  the  liquid  may  run  into  the  vessel  B,  on 
which  the  tube  is  soldered.  The  whole  apparatus  is  affixed 
to  a  sheet  of  tin-plate,  movable  in  two  slots  R  R.  The 
extent  of  movement  is  determined  by  two  stops  t  t,  so 
placed  that  when  the  base  of  the  apparatus  abuts  against 
one  of  them,  the  pipette  will  be  in  contact  with  the  sponge. 
When  it  strikes  the  other  it  will  be  directly  over  the  center 
of  the  neck  of  the  bottle. 

REMARKS. — The  precipitated  chloride  of  silver  must  be 
exposed  to  the  light  as  little  as  possible.     Sunlight  con- 


114  WET  ASSAYS. 

verts  the  chloride  into  a  sub-chloride,  liberating  chlorine, 
and  this  vitiates  the  results.  The  action  of  sunlight  may 
be  prevented  by  windows  of  yellow  glass,  which  excludes 
chemical  rays.  If  the  bullion  treated  contains  mercury, 
sunlight  will  not  blacken  the  combined  chlorides  ;  the  mer^ 
cury  may  be  held  in  solution  by  adding  10  gms.  of  acetate 
of  soda  containing  a  little  free  acetic  acid.  Test  for  the 
presence  of  mercury  by  standing  the  bottle  in  the  light.  The 
temperature  of  the  normal  solution  should  remain  the  same 
as  that  at  which  it  was  standardized.  The  most  convenient 
temperature  is  68°  F.,  and  the  solution  should  be  made 
and  kept  in  a  separate  room,  the  heat  of  which  can  be  reg- 
ulated by  a  good  thermometer. 

Despite  all  precautions  the  normal  solution  will  become 
stronger  in  time  through  evaporation  of  water.  This  will 
demand  correction,  and  in  regular  practice  it  is  customary 
to  take  a  certain  weight  of  pure  silver  and  subject  it  to  the 
same  operation  as  the  regular  assays.  The  latter  are  cor- 
rected according  to  the  indications  of  the  proof  assay. 
1.004  grammes  of  silver  is  a  convenient  weight  to  take. 

Example :  Suppose  we  have  added  to  a  check  of  1.004 
gms.  pure  silver,  100  c.c.  normal  and  3.5  c.c.  decime  salt. 
This  would  show  that  our  normal  is  too  strong,  and  in- 
stead of  making  the  proportion  in  the  preceding  example 
1.145  : 1.0045  : :  1000  :  x,  it  should  be  1.145  : 1.005  : :  1000  :  x. 
If  we  have  determined  by  evaporation  the  salt  in  one  c.c.,  we 
simply  divide  0.54167  by  the  weight  found,  and  we  have  the 
number  of  c.c.  of  concentrated  solution  to  be  diluted  to  100. 

The  presence  of  sulphide  of  silver  or  antimony,  lead,  and 
tin,  sometimes  interferes  in  making  the  silver  bullion  assay. 
The  first  two  may  be  removed  by  boiling  with  stronger  acid. 
For  the  latter  a  little  nitre  and  sulphuric  acid  will  make  a 


GOLD   BULLION. 


clear  solution.  (See  Report  of  the  Director  of  the  U.  S. 
Mint  for  1875). 

The  pure  silver  required  for  standardizing  and  check  as- 
says may  be  made  by  dissolving  tough  bar  silver  in  nitric 
acid,  and  precipitating  with  pure  hydrochloric  ;  the  white 
precipitate  being  well  washed,  and  fused  with  bi-  carbonate 
of  soda,  and  the  button  obtained  re-melted  with  borax  to 
toughen  and  purify  it. 

The  chloride  can  also  be  reduced  with  zinc  and  dilute 
sulphuric  acid,  and  the  fine  silver  obtained  melted  down 
with  borax  glass  ;  re-melting  to  purify. 


GOLD  BULLION. 

The  assay  of  gold  coin  and  bullion  comprises  two  deter- 
minations, a.  Base  metal,  b.  Gold.  The  difference  be- 
tween these  two  and  the  total  weight  of  bullion  gives  the 
amount  of  silver. 

a.  BASE  METAL:  CUPELLATIOX. — Weigh  out  0.500  gms. 
and  cupel  with  ten  times  its  weight  of  pure  lead  rolled  out 
into  a  sheet,  the  bullion  being  wrapped  in  it.  If  the  bul- 
lion contain  much  copper,  use  more  lead,  or  one-half  the 
amount  of  bullion. 

The  copper  is  oxidized  and  carried  into  the  cupel  by  the 
litharge,  leaving  a  button  of  gold,  and  silver  if  there  be 
any  present. 

A  check  assay  is  made  with  every  set  of  assays.  We 
employ  for  this  a  proof -alloy  containing  850  parts  of  gold, 
12  parts  of  copper,  and  the  rest  silver.  This  ought  to  lose 
by  cupellation  just  12  parts  of  copper.  It  may  lose  more 
or  less,  and  according  to  the  difference  one  way  or  other, 


t!6  WET  ASSAYS. 

we  correct  the  regular  assays  which  have  been  made  under 
the  same  conditions.  Suppose  the  check  assay  gave  11.8 
copper  instead  of  12.0,  the  proportion  of  copper  obtained  in 
each  of  the  regular  assays  must  then  be  increased  by  0.2 
thousanths,  or  vice  versa. 

£.  GOLD  :  PAETINO.  — Take  for  this  operation  0. 5  grammes 
of  the  alloy  and  add  twice  as  much  pure  silver  as  there  is 
gold  contained  in  the  alloy  used.  Wrap  the  alloy  and  sil- 
ver in  a  sheet  of  lead  and  cupel.  If  the  alloy  be  over  950 
fine,  add,  say  0.005  gms.  of  rolled  copper  to  toughen  the 
cornet.  The  button  obtained  from  cupellation  is  hammered 
on  the  anvil  to  flatten.  Three  blows  with  a  light  hammer 
will  suffice.  It  is  then  heated  to  redness  in  a  clay  anneal- 
ing cup,  and  passed  between  the  rolls  of  a  small  flattening 
mill.  When  rolled,  the  ribbon  is  again  annealed  and 
wound  into  a  cornet  or  spiral. 

The  cornet  is  subjected  to  the  action  of  nitric  acid  in  a 
glass  matrass  of  about  three  ounces  capacity  (Fig.  24). 
Acid  of  two  different  degrees  of  strength  is  employed.  The 
first  has  a  specific  gravity  of  1.16  (21°Beaume) ;  the  second 
a  gravity  of  1.26  (32°  Beaume).  If  very  strong  acid  were 
used  at  first  the  action  would  be  too  brisk  and  might  break 
up  the  cornet.  First  pour  on  the  acid  of  1.16  specific  grav- 
ity, and  heat  for  ten  minutes  ;  replace  this  with  acid  of  1.26 
specific  gravity,  and  boil  ten  minutes ;  decant,  and  make  a 
second  boiling  with  acid  of  the  same  strength  (1.26)  for 
another  ten  minutes.  A  gentle  boiling  is  intended,  and  not 
a  tumbling  about  of  the  cornet.  Finally  the  cornet  is 
washed,  the  flask  filled  completely  with  distilled  water, 
an  annealing-cup  placed  over  the  neck,  and  the  whole  is  in- 
verted. The  cornet  falls  into  the  cup,  the  flask  is  removed, 


GOLD   BULLION.  117 

the  water  decanted,  and  the  cornet  dried  and  annealed. 
The  weight  of  this  cornet  gives  the  amount  of  gold  in  the 
sample  assayed.  The  gold,  copper,  and  silver  are  reported 
in  thousandths.  A  fine  gold  proof  to  which  the  same 
amount  of  copper  has  been  added  as  in  the  assay,  should 
be  run  under  the  same  conditions,  as  a  check.  Where  a 
large  number  of  cornets  are  to  be  treated  at  once,  the  appa- 
ratus shown  in  Fig.  31  will  be  found  convenient.  It  con- 
sists of  a  number  of  small  platinum  cups,  arranged  in  a  tray 
of  the  same  metal,  which  can  be  set  inside  of  the  platinum 
vessel  (a).  This  is  covered  and  connected  with  an  arrange- 
ment for  condensing  the  acid  fumes. 

REMARKS. — The  government  uses  for  test  assay  of  gold 
coins,  an  alloy  of  gold  900,  copper  75,  and  silver  25  parts. 

Proof  gold  for  test  assays  can  be  made  by  dissolving  as 
pure  metal  as  obtainable,  in  aqua  regia,  diluting  the  solu- 
tion largely  and  allowing  it  to  stand  to  settle  any  chloride 
of  silver,  the  filtered  solution  being  then  concentrated  to 
crystallization,  diluted  with  pure  water,  and  the  gold  pre- 
cipitated with  oxalic  acid,  filtered  off,  well  washed,  dried 
and  fused  with  borax  and  nitre  ;  re-fusing  to  purify.  Sul- 
phate of  iron  may  be  used  in  place  of  oxalic  acid  for  precip- 
itation, but  tests  made  in  the  Royal  Mint,  London,  proves 
the  former  to  be  the  best. 

If  the  gold  contains  platinum,  the  amount  of  silver  present 
cannot  be  accurately  determined  by  the  cupellation  process. 

In  case  there  be  but  a  small  proportion  of  gold  in  the 
alloy  assayed,  the  exact  fineness  can  be  best  determined  by 
adding  sufficient  fine  gold  to  make  it  900  parts  in  the  1000. 

When  the  weight  of  the  cornet  is  ascertained,  the  weight 
of  fine  gold  added  may  be  deducted. 


FRONT  ELEVATI  ON 


SECTIONoNTHELlNEAJSi 


PUTINUM  CORNET 
CUP  , 

.  Size) 


PLATINUM  TRAY  TO  HOLD 

A3  CORNETS  (J-  NAT  SlZc) 


FIG.   31. 
PLATINUM  APPARATUS 

For  Parting  Gold  and  Silver,  as  used  in  the  Royal  Mint,  London. 


^  ASSAY.  119 


CHLORINATION  ASSAY. 

To  determine  the  percentage  of  chlorination,  weigh  out 
two  samples  of  the  chloridized  ore  or  "pulp,"  each  j^  A.T. 
Scorify  one  with  30  gms.  of  lead,  and  cupel.  Place  the  sec- 
ond sample  in  a  filter  paper  and  wash  with  a  strong  solution 
of  hyposulphite  of  soda  in  water  (two  pounds  to  the  gal- 
lon) until  all  the  chloride  of  silver  in  the  "  pulp  "  has  been 
dissolved.  This  can  be  determined  by  adding  a  drop  of  a 
solution  of  sulphide  of  sodium  in  water  to  a  test  sample  of 
the  filtrate.  When  no  black  precipitate  or  brown  color  is 
formed,  the  chloride  of  silver  is  all  dissolved,  and  the  desired 
point  has  been  reached.  Wash  the  residue  with  pure  water, 
dry  and  burn  the  filter  in  a  dish  or  scoop,  in  the  cupel  muffle. 
Mix  the  ashes  with  30  gms.  of  pure  lead,  scorify  and  cupel. 
The  calculation  can  best  be  shown  by  an  example  : 

The  "pulp"  untreated  gave  208  ozs.  of  silver  per  ton. 
The  "pulp"  treated          "      14    " 

still  remaining  in  the  ore  unchloridized.  Hence,  to  deter- 
mine the  percentage  of  silver  chloridized,  form  the  propor- 
tion :  208  :  (208—14)  :  :  100  :  x. 

Where  sulphate  of  silver  is  present  a  third  sample  leached 
with  hot  water  should  be  run  in  addition  to  the  two  gisren 
above,  the  residue  being  assayed  in  the  same  way.  By 
treating  three  samples,  the  amount  of  silver  present  as 
sulphate,  the  amount  contained  as  chloride,  and  the  total 
silver,  can  be  determined. 

In  the  West,  nearly  all  silver  reducing  works  make  these 
assays  every  day,  as  the  amount  of  chloridized  silver  is  all 
that  can  be  extracted  by  amalgamation. 

REMARKS.  —  This  method  is  sufficiently  accurate  to  check 


120  WET    ASSAYS. 

the  chlorination  of  the  ore,  and  with  proper  care  duplicate 
assays  are  unnecessary. 

The  operations  of  scorification  and  cupellation  are  con- 
ducted as  already  described  under  the  head  of  silver 
ores. 

The  success  of  the  process  depends  upon  the  care  taken 
in  washing. 


SCHEME  FOR  LEAD. 

Treat  two  gms.  finely  pulverized  ore  with  concentrated 
nitric  acid,  and  heat  until  the  residue  becomes  nearly  white, 
and  red  vapors  cease  to  be  evolved.  Add  a  few  drops  of 
sulphuric  acid  and  evaporate  to  dry  ness,  then  dilute  with 
water,  filter  and  wash  until  the  filtrate  shows  no  acid  reac- 
tion with  litmus  paper.  The  residue  will  contain  the  lead 
as  sulphate,  silica,  and  mixed  sulphates.  Wash  this 
off  the  filter  into  a  beaker  with  a  concentrated  solution 
of  neutral  carbonate  of  soda  and  digest  for  an  hour. 
Filter  off  and  wash  the  residue  of  carbonate  of  lead,  etc. 
Dissolve  in  acetic  acid,  and  precipitate  the  filtered  solu- 
tion with  just  sufficient  sulphuric  acid  to  ensure  complete 
precipitation.  Filter  off  the  separated  sulphate  of  lead, 
dry,  heat  to  redness,  and  weigh.  The  weight  of  the  sul- 
phate of  lead  multiplied  by  0.6832  will  give  the  metallic 
lead. 

i 

REMAKKS. — If  the  ore  contains  much  limestone  do  not 
carry  the  first  evaporation  too  far,  and  before  adding  sul- 
phuric acid,  dilute  with  water.  Use  dilute  sulphuric  acid. 
This  method  is  recommended  by  Percy,  and  is  used  with 


SCHEME   FOE   PLATINUM. 


success  at  Bleiberg  —  duplicates  agreeing  to  within   less 
than  0.2  of  one  per  cent. 


SCHEME  FOR  PLATINUM. 

Treat  one  gm.  of  ore  or  alloy,  with  hydrochloric  acid,  fil- 
ter and  wash.  This  will  separate  the  iron  and  soluble  con- 
stituents. Treat  the  residue  with  nitric  and  muriatic  acid, 
the  latter  being  in  excess,  and  digest  for  some  time — eight  to 
fifteen  hours.  Filter  and  wash.  The  residue  will  contain 
most  of  the  iridium  and  osmium.  The  solution  will  contain 
the  platinum  more  or  less  pure,  according  to  the  number 
of  other  metals  present  in  the  ore.  Evaporate  it  nearly  to 
dryness  and  add  twice  its  bulk  of  alcohol,  and  chloride  of 
ammonium  until  a  precipitate  ceases  to  form.  Filter,  wash, 
and  dry ;  then  transfer  filter  and  contents  to  a  porcelain 
crucible ;  cover  and  heat  gradually,  and  finally  intensely, 
cool,  and  weigh  the  residue  of  platinum  sponge. 

Alloys  containing  platinum,  gold,  silver,  iridosmine, 
and  base  metals  can  also  be  assayed  by  the  following 
method  : 

Take  alloy  200  mgs.,  pure  silver  150-200  mgs.  Wrap  in 
sheet  lead  and  cupel.  Weigh  the  button.  The  loss  is  base 
metal.  Flatten,  anneal,  and  roll  the  button  out  thin,  an- 
neal again,  and  make  into  a  cornet  as  in  gold  bullion  assay. 
Part  the  cornet  with  concentrated  sulphuric  acid,  boiling 
for  several  minutes.  Wash,  anneal,  and  weigh.  The  dif- 
ference between  this  weight  and  the  button  from  cupella- 
tion  is  the  silver  in  the  alloy  plus  the  silver  added.  Alloy 
the  weighed  cornet  with  12-15  times  its  weight  of  silver, 
roll  out,  anneal,  and  make  into  a  fresh  cornet,  then  part 


122  WET   ASSAYS. 

with  nitric  acid  sp.  gr.  1.16  and  afterward  with  nitric  acid 
sp.  gr.  1.26.  Wash,  anneal,  and  weigh.  Loss  equals  plati- 
num and  silver  added. 

Treat  the  residue  with  aqua  regia,  which  will  dissolve 
the  gold.  Wash,  dry,  and  weigh  the  iridosmine  which  re- 
mains. 

REMAKKS. — When  the  proportion  of  silver  in  a  button 
is  very  large,  the  nitric  acid  will  dissolve  the  platinum  also. 
The  above  methods  have  been  tried  with  success  on  vari- 
ous platinum  compounds,  and  for  practical  purposes  will 
be  found  sufficiently  close.  It  is,  however,  difficult  to 
dissolve  all  the  platinum  with  the  silver  and  separate  the 
iridosmine,  etc.  In  sponging  the  platinum,  it  should  be 
wrapped  in  paper  first,  and  covered  to  prevent  loss.  Care 
must  be  taken  to  drive  out  all  the  ammonia  salts,  by  rais- 
ing the  temperature  toward  the  last. 


SCHEME  FOR  ZI1STC. 

The  ore  may  contain  lead,  arsenic,  antimony,  sulphur, 
gold,  silver,  copper,  zinc,  manganese,  iron,  silica,  alumina, 
lime,  and  magnesia.  To  determine  the  zinc.  Weigh  out  one 
to  four  gms.  of  ore,  according  to  its  richness.  Treat  with 
ten  c.c.  nitric,  five  c.c.  muriatic,  and  ten  c.c.  sulphuric 
acid,  adding  each  separately  and  in  order,  increasing  the 
quantity  if  necessary.  All  the  acids  should  be  concentrated. 
Evaporate  nearly  to  dryness  in  a  porcelain  casserole  ;  mois- 
ten with  dilute  muriatic  acid,  and  dilute  with  water.  Pass 
sulphuretted  hydrogen  gas  through  the  solution  as  de- 
described  on  page  45.  Warm,  filter,  and  wash. 


RESIDUE  A 

Will  contain  the  lead,  ar- 
senic, antimony,  sulphur, 
gold,  silver,  silica,  and  most 


ZINC.  123 


FILTRATE  A 

Will  contain  the  zinc,  manganese,  iron,  alumina, 
and  magnesia.  Boil  with  one  or  two  crystals  of 
chlorate  of  potash,  nearly  neutralize  with  car- 


of  the  lime.  bonate  of  soda    until  a  reddish  color  appears ; 

boil  and  add  acetate  of  soda  (4  to  8  gms).     Boil 
RESIDUE  B 

for  ten  to  twenty  minutes,  filter  and  wash. 
Will   contain  the  iron   and 


FILTRATE  B 

alumina. 


Will  contain  the  manganese,  zinc,  and  magnesia. 
Add  acetic  acid,  warm  and  saturate  with  sulphuretted  hydrogen  gas,  and  fil- 
ter. Wash  carefully  with  sulphuretted  hydrogen  water  once  or  twice. 


RESIDUE  C 
Will  contain  zinc  and  sulphur. 


FILTRATE  C 
Manganese  and  magnesia. 


Dissolve  residue  C  on  the  filter  with  warm  hydrochloric  acid, 
add  a  little  chlorate  of  potash  to  the  solution,  and  boil.  Add 
carbonate  of  soda  until  a  precipitate  ceases  to  form.  Filter 
and  wash  the  precipitate,  dry  on  the  paper  and  ignite  in  a 
platinum  crucible.  Weigh  after  cooling.  Deduct  the 
weight  of  the  crucible  and  filter  paper  from  the  last  weight 
and  multiply  the  difference  by  0.8026.  The  product  will 
be  the  metallic  zinc. 
The  percentage  can  be  determined  by  the  formula.  Per- 


cent,  of  zinc= 


weight  of  ore  taken 

If  the  ore  contains  no  manganese,  instead  of  precipitat- 
ing filtrate  a  with  acetate  of  soda,  boil  it  with  two  or  three 
crystals  of  chlorate  of  potash,  and  add  ammonia  in  excess  ; 
the  residue  will  contain  the  iron  and  alumina,  the  filtrate 
the  zinc,  which-  can  be  determined  volumetrically  by  the 
following  method  : 

Prepare  a  solution  of  sulphide  of  sodium  in  water  (10 
gms.  to  1000  or  1200  c.c.  of  water),  and  standardize  with  a 
solution  of  zinc  made  by  dissolving  10  gms.  pure  zinc  in 


124  WET  ASSAYS. 

hydrochloric  acid  and  diluting  to  1  litre.  The  operation 
is  performed  by  measuring  off  50  c.c.  of  zinc  solution  in  a 
beaker,  adding  ammonia  until  the  precipitate  is  re-dissolved, 
then  400  c.c.  of  water ;  afterward  running  in  the  sulphide 
of  sodium  solution  from  a  pipette  until  a  drop  of  the 
zinc  solution  tested  with  chloride  of  nickel  on  a  porcelain 
plate, turns  blackish  gray.  Note  the  number  of  c.c.  of  sul- 
phide of  sodium  used,  and  repeat  to  be  certain.  Knowing 
the  amount  of  zinc  in  the  solution,  the  value  of  the  sulphide 
of  sodium  solution  per  c.c.  is  very  easily  calculated.  This 
done,  the  ammonia  solution  of  zinc  from  filtrate  a  can  be 
divided  and  tested  in  the  same  manner. 

Calculation.  The  number  of  c.c.  of  sodium  solution 
employed  multiplied  by  the  value  per  c.  c.  gives  the  amount 

of  zinc=Z.     ™-v  ,  .    *     — —i =the  per  cent,  of  zinc. 

Weight  of  ore  taken 

REMARKS. — A  silver  ore  containing  sulphide  of  zinc  was 
treated  by  the  first  method,  the  assays  being  made  in  du- 
plicate : 

No.  1  gave 2. 380  per  cent,  metallic  zinc. 

"     2     "  ..2.367         "  "  " 


DETERMINATION  OF  BISMUTH  IN  AN  ALLOY. 

Weigh  out  two  gins,  of  the  alloy,  and  treat  with  concen- 
trated nitric  acid  until  action  ceases.  Evaporate  to  dryness, 
add  50  to  100  drops  of  strong  sulphuric  acid.  Mix  with  a 
glass  rod,  and  evaporate  to  dryness.  Add  water  with  a  few 
drops  of  sulphuric  acid  and  boil.  Filter,  and  to  the  solution 
add  an  excess  of  carbonate  of  ammonia.  Collect  the  pre- 
cipitated oxide  of  bismuth  on  a  lilter,  wash,  and  dry.  Sepa- 
rate carefully  from  the  lilter,  ignite  in  a  porcelain  crucible 


TIN.  125 

and  weigh.     Every  100  parts  of   the  weight  found  corres- 
ponds to  89. 87  of  metallic  bismuth.     (See  Mitchell,  p.  642.) 

REMARKS. — The  bismuth  may  also  be  precipitated  from 
the  prepared  solution  by  either  lead,  or  copper  ;  and  after 
washing  and  drying,  be  weighed  in  a  metallic  form,  or  re- 
dissolved  and  precipitated  as  above,  In  this  case  copper 
will  be  the  best  precipitant. 


DETERMINATION  OF  TIN  IN  THE  WET  WAY. 

The  various  methods  that  have  been  employed  for  the  de- 
termination of  tin  in  the  wet  way  may  be  classed  under  two 
heads : 

a.  The  substance  is  an  ore.      This  may  consist  of  an 
oxide  or  sulphide  of  tin,  and  be  associated  with  iron,  cop- 
per, zinc,   bismuth,  arsenic,  antimony,   manganese,   silica, 
Ume,   magnesia,  and  alumina ;    occasionally  molybdenum, 
tungstic,  tantalic  or  niobic  acids. 

b.  The  substance  is  an  alloy,  which  may  contain  iron, 
copper,    zinc,  bismuth,  arsenic,  antimony,    tungsten,    and 
molybdenum. 

a.  The  substance  is  an  ore :  Sample  and  pulverize  finely, 
1.  If  the  ore  contain  volatile  ingredients,  roast  as  in  the 
dry  assay  and  treat  the  residue  with  nitro-hydrochloric  acid 
(cone.),  (3  parts  of  hydrochloric  to  1  of  nitric),  to  dissolve 
iron,  copper,  etc.  Boil  nearly  to  dry  ness,  cool,  dilute  with 
water  and  digest.  Filter.  The  residue  will  contain  the 
oxide  of  tin  and  silica,  possibly  the  tungstic  acid,  etc. 
Wash,  and  if  tungstic  acid  is  suspected,  digest  with  caus- 
tic ammonia  for  about  one  hour.  Filter,  wash,  dry,  and 


126  WET  ASSAYS. 

treat  the  residue  by  fire  assay,  or  by  one  of  the  methods 
given  below.  Instead  of  treating  the  roasted  ore  with  acids, 
it  may  be  fused  with  bi-sulphate  of  potash  in  excess,  which 
decomposes  the  silicates  in  the  ore  and  dissolves  the  bases; 
the  fused  mass  treated  with  water  and  hydrochloric  acid, 
the  residue  filtered  off,  washed,  dried,  and  treated  by 
dry  assay  or  wet,  as  the  case  may  be.  The  addition  of  cry- 
olite or  fluoride  of  potassium  in  the  fusion  with  bi-sulphate 
of  potash  gives  good  results. 

2.     If  the  ore  is  pure  or  has  been  purified. 

Method  by  fusion  with  sulphur :  Weigh  out  one  gm.  and 
mix  with  five  gms.  of  powdered  sulphur,  and  five  gms.  of 
dry  carbonate  of  soda.  Place  the  mixture  in  a  porcelain 
crucible,  cover  and  heat  over  a  Bunsen  burner,  or  alcohol 
lamp,  until  liquid.  Keep  fused  for  ten  or  fifteen  minutes  ; 
cool  and  treat  the  fused  mass  with  water,  filter  and  wash. 
Test  the  residue  for  tin  with  the  blowpipe,  and  if  any  be 
present  re-fuse  and  add  the  solution  to  the  one  obtained  in 
the  first  fusion. 

Place  the  solutions  in  a  large  beaker,  and  treat  with  dilute 
sulphuric  or  hydrochloric  acid  until  a  precipitate  ceases  to 
form;  boil,  filter  by  decantation,  and  wash  with  sulphu- 
retted hydrogen  water.  Dry  the  residue  and  ignite  in  a 
weighed  porcelain  crucible,  to  expel  sulphur,  adding  a  few 
drops  of  nitric  acid  to  oxidize  toward  the  last.  Weigh 
until  constant.  The  addition  of  a  little  carbonate  of  am- 
monia in  the  ignition  will  help  to  expel  any  sulphuric  acid. 
The  ignited  residue  consists  of  binoxide  of  tin  and  silica ; 
if  great  accuracy  is  required,  it  should  be  purified  either  by 
heating  with  fluoride  of  ammonium  until  the  weight  is  con- 
stant, or  reducing  the  binoxide  of  tin  with  hydrogen,  dis- 
solving the  metal  produced  in  hydrochloric  acid,  washing 


TIN.  137 

and  weighing  the  residue.    The  loss  represents  the  binoxide 

59 

of  tin.     The  weight  of  binoxide  found,  multiplied  by  ^ 

7  o 

gives  the  metallic  tin. 

Coal  gas  may  be  used  instead  of  hydrogen,  the  weighed 
precipitate  being  placed  in  the  bulb  of  a  small  chloride  of 
calcium  tube,  through  which  the  gas  is  passed,  the  bulb 
being  heated. 

Method  by  fusion  with  caustic  potash  : 

Weigh  out  one  gramme  and  fuse  with  six  to  ten  gms.  of 
caustic  potash  in  a  silver  crucible.  The  potash  being  placed 
in  the  crucible  with  its  own  weight  of  water,  the  ore  stirred 
in,  and  the  whole  mass  evaporated  to  dryness,  and  then 
heated  for  one  half  hour,  until  fusion  is  complete.  Dissolve 
the  fused  mass  in  water  and  hydrochloric  acid,  and  boil ; 
any  tin  ore  unacted  upon,  filter  off  and  re-fuse.  Evaporate 
to  dryness,  moisten  with  hydrochloric  acid  and  water,  di- 
gest, filter  and  wash.  The  solution  will  contain  the  tin  free 
from  silica,  tungstic  acid,  etc. 

The  tin  can  be  precipitated  from  the  solution  with  zinc,  in 
the  metallic  state,  collected,  washed  and  weighed,  or  it  may 
be  precipitated  with  sulphuretted  hydrogen  and  the  pre- 
cipitate filtered  off,  washed,  ignited,  and  weighed  as  bin- 
oxide. 

In  cases  where  the  ore  has  been  purified  with  acids,  or  by 
fusion  with  bisulphate  of  potash,  the  silica  may  be  expelled 
with  fluoride  of  ammonium  until  the  weight  is  constant, 
and  the  residue  weighed  as  binoxide.  The  results  are, 
however,  liable  to  be  too  high. 

I).  The  substance  is  an  alloy. 

1.  Dissolve  in  hot  hydrochloric  acid,  filter,  and  wash. 
Precipitate  the  filtrate  with  zinc.  Collect  the  precipi- 
tated metals,  dry,  and  ignite;  treat  with  concentrated 


128  WET   ASSAYS. 

nitric  acid  and  wash.     Dry  the  residue,  and  weigh  as 
binoxide. 

2.  Oxidize  the  finely  divided  alloy  (filings)  with  nitric 
acid,  sp.  gr.  1.3.  Add  water,  digest  and  filter,  wash,  ig- 
nite, and  weigh  the  residue  as  binoxide  of  tin. 

REMARKS. — Slags  which  contain  stannates.  Pulverize, 
and  afterwards  digest  with  water,  filter,  and  treat  the  solu- 
tion with  dilute  sulphuric  acid. 

The  best  way  is  to  neutralize  the  solution  with  ammonia, 
add  a  little  hydrochloric  acid  to  dissolve  any  precipitate 
formed,  then  the  sulphuric  acid,  and  dilute.  Allow  to 
stand  for  several  hours  before  filtering  off  the  precipitate 
formed.  Ignite  and  weigh  as  binoxide.  Watts'  Dictionary 
of  Chemistry,  Vol.  5,  page  811. 

Comparison  of  results  obtained  by  various  methods  in 
tne  assay  laboratory. 


ORE. 


METHOD  BT  FUSION  METHOD  BY  METHOD  WITH 

WITH  SULPHUR.  FLUORIDE.  HYDROGEN. 


Durango,  76.8  76.8 

"  76.3  76.4 

"  76.2  76.4 

Locality  unknown,  74.8  75.5  75.0 

"  "  74.7  75.7 


SCHEME  FOR  COPPER. 

Roast  five  gms.  of  the  finely  powdered  ore  with  the  addi- 
tion of  a  little  charcoal,  and  carbonate  of  ammonia  toward 
the  last.  Treat  the  residue  in  a  covered  casserole,  with  five 
c.c.  hydrochloric,  ten  c.c.  nitric,  and  ten  c.c.  sulphuric  acid, 
concentrated,  and  added  in  order.  Evaporate  until  heavy 
white  fumes  come  off  in  excess.  Cool,  dilute  with  a  little 
water  and  digest,  filter,  and  wash  the  residue  until  the  fil- 


COPPEE.  129 

trate  does  not  turn  black  with  sulphuretted  hydrogen  solu- 
tion.    Test  the  residue  with  the  blowpipe  for  copper. 

The  solution  will  contain  the  copper  as  sulphate,  and  can 
be  treated  in  several  ways.  The  best  are : 

a.  Precipitation  by  the  battery. 

b.  Precipitation  by  zinc  or  iron. 

c.  Volumetric  determination. 

Divide  the  solution  in  five  equal  parts  by  volume. 

•a.  Precipitation  by  the  battery. 

Place  the  acid  solution  of  copper  in  a  weighed  platinum 
dish  ;  set  the  dish  upon  a  spiral  of  copper  wire  connecting 
the  zinc  element  of  a  Bunsen  cell,  and  have  in  the  solution 
a  piece  of  clean  platinum  foil  suspended  from  another 
wire  connecting  with  the  carbon  element.  Test  for  the 
complete  precipitation  of  the  copper  by  taking  out  a  little 
of  the  solution  and  adding  sulphuretted  hydrogen ;  if  no 
color  is  observed  the  precipitation  is  complete.  Decant 
the  fluid  from  the  red  precipitate  of  copper,  wash  once  with 
water,  and  twice  with  alcohol.  Dry  by  holding  in  the  hand 
over  a  flame,  and  weigh.  This  weight,  less  the  weight  of 
the  dish,  equals  metallic  copper.  The  operation  of  drying 
and  weighing  must  be  conducted  as  quickly  as  possible. 

5.  Precipitation  by  zinc  or  iron. 

Pour  one  part  of  the  solution  of  copper  in  a  porcelain 
dish,  in  which  is  placed  a  Avcighed  slip  of  platinum  foil; 
rest  upon  the  latter  a  pieco  of  pure  zinc  (Leliigh  zinc  will 
do),  and  add  dilute  sulphuric  acid  until  fumes  cease  to 
come  off  and  the  zinc  is  dissolved.  The  solution  should 
then  be  clear  and  give  no  color  with  sulphuretted  hydrogen. 
Pour  off  the  liquid,  press  the  copper  together,  and  wash 
with  water  and  alcohol ;  dry  and  weigh  the  copper  and 
foil.  This  weight,  less  that  of  the  foil,  gives  the  copper. 


130  WET  ASSAYS. 

The  precipitation  by  iron  is  conducted  in  much  the  same 
manner,  save  that  the  solution  should  be  nearly  neutral, 
and  no  platinum  foil  is  required.  The  iron  used  should  be 
clean  and  pure  ;  it  may  be  either  sheet  or  wire. 

c.  Volumetric  determination. 

Take  one  part  of  the  prepared  solution  of  copper  and  add 
ammonia  in  excess  until  the  precipitate  formed  is  dissolved  ; 
the  solution  should  be  a  deep  blue.  Then  titrate  with  a 
prepared  solution  of  cyanide  of  potassium  until  tho  blue 
color  disappears.  The  number  of  c.c.  of  cyanide  used,  indi- 
cates the  amount  of  copper  present.  Tho  cyanide  solution 
is  made  by  dissolving  sixty  to  seventy  gms.  commercial 
cyanide  of  potassium  in  two  quarts  of  water,  and  standard- 
izing it  with  a  solution  of  pure  copper,  of  known  value. 
This  is  made  by  dissolving  five  gms  of  pure  copper  in  nitric 
acid,  boiling  and  diluting  to  one  litre.  A  portion  of  this 
solution  can  then  be  treated  with  ammonia  and  cyanide, 
and  the  value  of  the  latter  in  copper  per  c.c.  ascertained. 
Should  zinc,  nickel,  cobalt,  or  manganese  be  present  in 
the  ore  treated,  it  is  well  to  precipitate  the  copper  with 
zinc  in  a  porcelain  dish,  wash  with  water,  and  re-dissolve 
in  nitric  acid.  Then  add  ammonia  and  proceed  with 
the  titration.  The  solution  of  cyanide  should  be  kept 
in  a  green  bottle,  tightly  stoppered,  and  away  from  the 
light. 

REMARKS. — Determinations  of  copper  in  a  mixture  of  iron 
and  copper  pyrites  gave,  by  precipitation  with  sheet  iron, 
16.6  per  cent.  ;  by  volumetric  estimation  with  cyanide  solu- 
tion 16.53  and  16.35  per  cent.  Another  sample  gave  8.4 
and  8.6  per  cent.,  and  a  third  specimen  gave,  by  battery, 
i.3  per  cent.,  with  zinc,  1.3  per  cent. 


IRON.  131 

SCHEME  FOR  IRON. 

VOLUMETRIC.—  Weigh,  out  1  gm.  of  the  finely  powdered 
ore.  Fuse  in  a  platinum  or  porcelain  crucible,  with.  4  to  6 
gins,  carbonate  of  soda  and  J  to  1  gm.  of  nitrate  of  soda, 
well  mixed,  until  the  whole  mass  is  in  quiet  fusion.  Then 
cool  and  dissolve  in  a  casserole  with  water,  acidulating 
gradually  with  hydrochloric  acid,  until  gas  ceases  to  come 
oil.  Keep  covered  to  prevent  loss.  Heat  for  some  time, 
filter  and  wash. 

Treat  the  filtrate  with  ammonia  until  a  precipitate  ceases 
to  form ;  boil,  filter,  and  wash  once  or  twice,  and  then  dis- 
solve the  precipitate  in  dilute  sulphuric  acid  on  the  filter, 
and  wash.  The  solution  containing  the  iron  as  sulphate  is 
placed  in  a  6  oz.  bottle  with  a  clean  strip  of  platinum  foil 
and  a  small  piece  of  amalgamated  zinc,  free  from  iron. 
Allow  it  to  stand  several  hours,  then  transfer  to  a  large 
beaker  and  titrate  with  a  standard  solution  of  permangan- 
ate of  potash  prepared  as  follows  :  Make  a  solution  of  crys- 
talline permanganate  of  potash  in  water  and  standardize 
it  with,  a  solution  of  pure  sulphate  of  iron  of  known  value. 

The  latter  is  prepared  by  dissolving  0.2  gms.  of  fine  iron 
piano-forte  wire,  well  cleaned,  in  a  four  ounce  flask  with 
dilute  sulphuric  acid.  The  flask  should  be  closed  so  that 
the  gas  evolved  can  pass  out  and  no  air  enter.  To  effect 
this,  stop  the  flask  with  a  cork  in  which  is  fitted  a  glass  tube 
about  two  inches  long,  on  the  end  of  which  is  a  piece  of 
rubber  tubing  closed  at  the  extremity  with,  a  small  piece  of 
glass  rod  and  slit  on  one  side.  In  this  way  a  valve  is  formed 
which  allows  the  gas  to  escape.  Heat  just  enough  to  dis- 
solve the  wire,  and  when  this  is  effected  decant  into  a  me- 
dium sized  beaker,  wash  the  flask  out,  adding  the  wash 


132  WET  ASSAYS. 

water  to  the  solution  in  the  beaker  (use  cold  water) ;  then 
add  5  to  10  c.c.  dilute  sulphuric  acid,  and  titrate  with  the 
permanganate  solution,  adding  one  c.c.  at  a  time  from  a 
graduated  burette. 

The  weight  of  the  iron  taken,  multiplied  by  0.997,=  the 
weight  of  pure  metallic  iron  to  which  the  cubic  centimeters 
of  permanganate  used  is  equivalent.  All  that  is  necessary 
is  to  find  the  value  of  1  c.c.  of  permanganate,  and  in  testing 
an  ore  multiply  it  by  the  number  of  c.c.  used.  The  pro- 
duct equals  the  metallic  iron  in  the  ore. 

The  presence  of  titanium  interferes  with  this  method. 

In  this  case  the  solution  in  the  reduction  bottle  will  have 
a  pink  tinge  after'  standing.  To  separate  the  iron  and 
titanic  acid,  dry,  and  ignite  the  ammonia  precipitate  in  a 
glass  tube  which  can  be  heated  strongly  over  a  burner,  hy- 
drogen (street  gas)  being  passed  through  the  tube  ;  dissolve 
the  iron  and  proceed  as  above.  The  same  precautions  should 
be  observed  in  keeping  the  permanganate  solution  as  in  the 
case  of  the  cyanide.  See  scheme  for  copper. 


REMABKS — A  sample  o±  magnetite  and  hematite  gave  by 
this  method,  duplicate  assays  being  made, 

No.  1 52.304  per  cent.  iron. 

No.  2 52.416        "  " 

The  ore  contained  no  titanic  acid. 


SCHEME  FOR  MANGANESE. 

Manganese  occurs  in  an  oxidized  form,  and  its  principal 
ores  are 


MANGANESE.  133 

Pyrolusite  (MnO2) available  oxygen =18  per  cent. 

Braunite  (2Mn3O4+MnSiO4).       "  "      =10 

Manganite  (H2Mn2O4) "  "      =9 

Psilomelane  (MnO  +  4MnO2).       "  "       =9       " 

Hausmannite  (Mn3O4) "  "      =  6.8    " 

Wad  (H2Mn2O5) "  "      variable. 

The  quantity  of  oxygen  which  an  ore  of  manganese  is 
capable  of  yielding  generally  regulates  its  commercial 
value  ;  hence,  it  is  only  necessary  to  determine  the  amount 
of  binoxide  contained,  which  can  be  arrived  at  very  easily 
by  the  following  method,  which  is  sufficiently  accurate  for 
practical  purposes. 

ASSAY. — Weigh  out  1  to  2  gms.  of  the  finely  pulverized 
ore,  place  in  a  small  flask,  and  add  from  5  to  7  gms.  of  neu- 
tral oxalate  of  potash  in  powder,  and  a  little  water.  Close 
the  flask  with  a  plug  of  cotton  and  weigh.  Then  add  about 
30  c.c.  of  sulphuric  acid,  a  little  at  a  time.  The  sulphuric 
acid  should  be  weighed  in  a  small  flask,  which  should  be 
again  weighed  when  empty,  to  determine  the  actual  weight 
of  sulphuric  acid  added  to  the  ore.  When  effervescence 
has  ceased,  heat  the  flask  containing  the  ore  gently  until 
every  trace  of  black  powder  in  the  same  has  disappeared. 
Cool  and  weigh.  The  amount  of  peroxide  of  manganese 
can  be  estimated  from  the  carbonic  acid  driven  off,  as  fol- 
lows :  Deduct  the  weight  of  the  flask  and  residue  from  the 
sum  of  the  first  weight  and  the  sulphuric  acid  used,  and 
multiply  the  difference  by  0.9887,  the  product  will  be  the 
amount  of  binoxide  of  manganese  contained  in  the  ore 
taken. 

REMAKKS. — When  the  ore  contains  carbonates  (which  can 
be  ascertained  by  testing  with  nitric  acid),  after  weighing 
out  the  ore,  treat  it  with  a  solution  of  one  part  of  sulphuric 


134  WET  ASSAYS. 

acid  to  five  parts  of  water,  until  the  carbonates  are  decom- 
posed. Weigh,  and  then  add  the  weighed  oxalate  of  potash 
and  more  acid. 

The  process  given  above,  in  order  to  be  perfectly  accurate, 
should  be  performed  in  an  air-tight  apparatus  with  the 
greatest  care,  so  that  nothing  but  carbonic  acid  can  escape, 
and  no  moist  air  enter.  See  Fresenius'  Quantitative  Analy- 
sis, London  edition,  p.  615. 

A  sample  of  manganese  ore  treated  by  this  method  gave 
64  per  cent,  of  binoxide.  The  same  sample  gave  63.9  per 
cent,  of  binoxide  by  determining  the  metallic  manganese, 
and  calculating  the  amount  of  oxide  it  would  form.  For 
this  test,  however,  the  apparatus  was  nearly  air-tight,  and 
a  little  more  perfect  than  the  one  described  above  ;  but  on 
the  same  principle. 

DETERMINATION  OF  NICKEL. 

Weigh  out  one  or  two  gms.  of  ore  and  roast  carefully, 
adding  charcoal,  and  carbonate  of  ammonia  toward  the  end 
of  the  operation.  Treat  the  roasted  ore  with  hydrochloric 
and  nitric  acids,  as  in  the  method  for  copper.  Cool,  and 
add  water  and  hydrochloric  acid.  Pass  sulphuretted  hy- 
drogen through  the  solution ;  warm,  filter,  and  wash.  Boil 
the  filtrate  with  one  or  two  crystals  of  chlorate  of  potash 
to  expel  excess  of  sulphuretted  hydrogen,  and  to  convert 
the  iron  present  into  a  sesqui-salt.  Treat  with  ammonia  in 
excess ;  boil,  filter,  and  wash.  The  solution  will  contain 
the  nickel  as  chloride.  Allow  it  to  stand  three  or  four 
hours,  and  filter  off  any  precipitate  formed  ;  evaporate  to 
dryness,  take  up  with  sulphuric  acid,  add  excess  of  am- 
monia and  place  the  solution  in  a  platinum  dish,  and 


SULPHUR.  135 

treat  as  in  the  determination  of  copper  by  the  battery, 
keeping  the  solution  ammoniacal  instead  of  acid. 

REMARKS. — The  smallest  amount  of  nickel  determined 
by  this  method  was  0.12  per  cent.  For  practical  purposes 
it  will  be  found  sufficiently  accurate,  but  is  liable  to  error 
in  the  separation  of  the  iron,  some  of  the  nickel  being  re- 
tained in  the  bulky  precipitate  formed  ;  this  may  be  pre- 
vented to  some  extent  by  dissolving  and  reprecipitating 
the  iron. 

SCHEME  FOR  SULPHUR. 

SOURCES. — Native  sulphur,  and  sulphides  of  the  metals, 
more  or  less  pure.  The  sulphide  of  iron  (pyrite)  (FeS2), 
being  most  used. 

ASSAY. — This  is  made  by  distillation,  and  in  the  wet  way, 
the  latter  is  the  best. 

To  conduct  the  first,  weigh  out  a  portion  of  the  finely  pul- 
verized ore  and  heat  it  in  a  retort,  which  should  be  fur- 
nished with  a  receiver  to  collect  the  sublimed  sulphur.  The 
retort  may  be  of  glass  if  the  ore  is  sulphurous  earth,  but 
must  be  of  iron,  if  pyrites  ;  the  latter  should  also  be  mixed 
with  sand,  to  prevent  its  fusing  together.  The  heat  for 
pyrites  should  be  full  red. 

The  product  of  distillation  is  weighed  and  should  be 
examined  by  the  wet  way  to  determine  its  purity  ;  hence  it 
is  generally  better  to  test  the  ore  by  this  method  at  once. 
Weigh  out  one  gm.  of  the  finely  pulverized  ore  and  fuse 
with  equal  weights  of  carbonate  of  soda  and  nitre,  using  a 
platinum  crucible,  and  adding  the  mixture  a  little  at  a 
time.  Keep  the  crucible  covered.  Dissolve  in  water,  filter, 


136  WET   ASSAYS. 

and  wash.  If  -the  residue  contains  sulphur,  repeat  the 
operation.  Combine  the  solutions,  add  a  little  hydro- 
chloric  acid,  and  then  chloride  of  barium  in  slight  excess, 
heat  for  a  few  moments,  and  allow  the  precipitate  to  settle. 
Pour  off  the  liquid  through  a  filter,  and  wash  once  with 
dilute  hydrochloric  acid  and  water,  afterwards  with  hot 
water.  Dry  and  ignite  the  residue  in  a  weighed  porcelain 
crucible.  Multiply  the  weight  of  the  precipitate  less  that 
of  the  filter  ash  by  TT?  ;  the  product  equals  the  weight  of 


sulphur  in  the  sample  taken. 

REMAKKS.  —  A  sample  tested  by  the  latter  method  gave 
32.52  per  cent,  and  32.55  per  cent,  of  sulphur  ;  two  separate 
weighings  being  made  for  the  analysis,  and  the  precipitates 
tested  to  determine  their  purity. 


PART  IV. 

TABLES  AND  REFERENCES 


PRECIOUS   STONES. 


139 


rOTNIVERsi 

'ES^^FOftNl* 


PRECIOUS   STO 

ARRANGED   ACCORDING  TO   HARDNESS. 


NAME. 

COLOR. 

HARD- 
NESS. 

SPECIFIC 
GRAVITY. 

ACTION  OF 
ACIDS. 

BLOWPIPE    CHARAC- 
TERISTICS. 

Diamond. 

Colorless,    smoky, 
yellow,  green, 
blue,  and  black. 

10. 

3.5 

Not  acted  on. 

Burns  at  an  intense 
heat,  without 
residue. 

Sapphire 
(Corundum). 

Colorless,  blue,  red, 
yellow,  gray,  and 
brown. 

9. 

3.9  to  4 

Insoluble. 

Infusible. 

Topaz. 

Colorless,  yellow, 
blue,  greenish- 
blue. 

8. 

3.5 

Not  acted  on. 

Infusible,  cracks  at 
a  high  heat. 

Ruby  (Spinel). 

Red,  blue,  green, 
yellow,   white,  and 
black. 

8. 

3.5  to  4.1 

Insoluble  in  hy- 
drochloric acid. 
Partly  soluble 
in  sulphuric 
acid. 

Infusible,  changes 
color. 

Emerald  (Aqua- 
marine,  Beryl). 

Green,  blue,  yellow, 
red,  and  white. 

7.5  to  8 

2.6  to  2.7 

Not  acted  on. 

Fuses  with  difficul- 
ty on  the  edges. 

Zircon. 

Colorless,  yellow, 
red,  brown, 
pink,  and  green. 

7.5 

4.  to  4.7 

Insoluble. 

Infusible. 

Agate,    Jasper, 
Amethyst, 
Onyx,  etc. 

(Quartz). 

Colorless,  white, 
black,  red,  and 
green. 

7. 

2.5  to  2.7 

Insoluble. 

Infusible,  except 
with  carbonate  of 
soda. 

Garnet. 

Red,  brown,  yellow, 
white,  green,  and 
black. 

6.5  to  7.5 

3.15  to  4 

Imperfectly  sol- 
uble. 

Fusible. 

Turquois. 

Blue,  white,  yellow, 
and  red. 

6. 

2.6  to  2.8 

Soluble. 

Infusible. 

Lapis-Lazuli. 

Blue,     red,    green, 
and  colorless. 

5.  5  to  5 

2.3  to  2.4 

Gelatinizes. 

Fuses  with  intumes- 
cence and  gives  a 
white  bead. 

Opal. 

Brown,  green,   and 
gray. 

5.5  to  6.5 

1.9  to  2.3 

More  or  less  sol- 
uble. 

Infusible,  gives  off 
water  and  be- 
comes opaque. 

Malachite. 

Bright  green. 

3.5  to  4 

3.7to4 

Soluble  with  ef- 
fervescence. 

Gives  off  water  and 

Fuses. 

SCALE  OF  HARDNESS. 

1.  Easily  scratched  with  the  nail. 

2.  Not  easily  scratched  with  the  nail.     Does  not  scratch 
a  copper  coin. 


140 


TABLES   AND   KEFERENCE8. 


3.  Scratches  and  is  scratched  by  a  copper  coin. 

4.  Not  scratched  by  a  copper  coin ;    does  not  scratch 
glass. 

5.  Scratches  glass  with  difficulty  ;   easily  scratched  with 
the  knife. 

6.  Scratches  glass  easily.      Not  easily  scratched  by  the 
knife. 

7.  Not  scratched  by  the  knife ;  yields  with  difficulty  to 
the  file. 

8.  Harder  than  flint. 

9.  Harder  still. 

10.  Diamond. 

« 

METALS— CHARACTERISTICS. 

INCLUDING   C  A  EBON   AND    SULPHUR. 


METAL. 

COLOR. 

HARDNESS. 

SPECIFIC 
GRAVITY. 

BEST  GOL- 
VENTS. 

ON  CHARCOAL 
BEFORE  THE 
BLOWPIPE. 

FUSIBILITY, 
CENTIGRADE. 

Lead. 

Bluish,  malle 
able. 

1.5 

11.45 

Nitric  or 
Muriatic. 

Fuses  and 
gives  a  yellow 
coat. 

334° 

Antimony. 

Bluish-white 
brittle. 

3-3.5 

6.8 

Aqua   regia 

Fuses  and 
gives  off 
white  fumes. 

425°—  450° 

Silver. 

White,  malle- 
able. 

2.5—3 

10.5—11.1 

Nitric  and 
sulphuric. 

Fuses,  gives 
reddish  coat 
with  long 
blowing. 

1000° 

Gold 

Yellow,    mal- 
leable. 

2.5—3 

19—20 

Aqua   regia 

Fuses  to  a 
button. 

1200° 

Platinum. 

Whitish  to 
steel-gray, 
malleable. 

4-4.5 

16—21 

Aqua   regia 

Infusible. 

In  flame  ol 
oxy.  h.  blp 

Zinc. 

Bluish-white, 
malleable, 
brittle. 

2. 

6.8-7.2 

All  acids. 

Oxidizes  and 
gives  a  white 
coat. 

412» 

Mercury. 

Tin-white, 
liquid. 

—1 

13.5 

Nitric. 

Volatilizes. 

Solid  at 
-39.4° 

Bismuth. 

Reddish  to 
silver  white, 
brittle. 

2—3.5 

9.7 

Nitric. 

Fuses  and 
gives  an  or- 
ange yellow 
coat. 

268.3° 

Tin. 

Like  silver, 
more  bluish, 
malleable. 

4—5 

7.28 

Muriatic. 
Sulphuric. 

Gives  metal- 
lic globule 
and  white 
coat. 

228' 

C°PP-       l    KeabTlle- 

2.5—3 

8.9 

Cone,  acids. 

Can  be  fused 
to  a  bead. 

1100- 

METALS— CHARACTERISTICS. 


141 


METALS. 

COLOR. 

HARDNESS. 

SPECIFIC 
GRAVITY. 

BEST   SOL- 
VENTS. 

ON  CHARCOAL, 
BEFORE  THE 
BLOWPIPE. 

FUSIBILITY, 
CENTIGRADE. 

Iron. 

Gray,  malle- 
able, mag- 
netic. 

4—5 

7.3—7.8 

All  acids. 

Infusible. 

Highest  heat 
of  Forge. 

Manganese. 

Grayish- 
white,  brittle. 

9-10 

7.1—8.01 

Nitric,  sul- 
phuric, mu- 
riatic. 

Infusible. 

« 

Nickel. 

Silver-white, 
malleable, 
magnetic. 

5—6 

8.2—8.7 

Nitric. 

Infusible, 

» 

Cobalt. 

Steel-gray    to 
red.  mag- 
netic. 

5-6 

8.5—8.7 

Nitric. 

Infusible. 

H 

Carbon. 

Colorless  to 
Black. 

Variable. 

Variable. 

Insoluble. 

Infusible- 
burns. 

Infusible. 

Sulphur. 

Yellow,  red- 
dish, greeu- 
ish,  brittle. 

1—2.5 

2.00 

Oil  of  Tur- 
pentine,etc. 

Melts  and 
gives  off  sul- 
phurous acid. 

Ill0—  114° 

The  value  of  the  various  metals  changes  according  to  the 
production  and  demand,  save  in  the  case  of  gold  which  has 
a  standard  value  of  twenty  dollars  and  sixty-seven  cents 
per  Troy  ounce  in  gold  coin,  when  perfectly  pure  ;  the  price 
being  determined  as  follows : 

By  the  laws  of  the  United  States  the  composition  of  the 
gold  coins  for  every  one  hundred  parts,  by  weight,  is  90 
parts  of  pure  gold  and  10  parts  of  alloy. 

Eight  hundred  dollars  in  U.  S.  gold  coin  weighs  43  ounces 

Troy, of  this  weight  must,  therefore,  be  pure  gold= 

800 

38.7  ounces.  ^-^  =  20.6718  dollars;  this  then  is  the    coin 

oo.7 

value  of  one  ounce. 

Before  the  immense  production  of  silver  depreciated  the 
cost  of  that  metal,  a  similar  calculation  gave  its  value  in 
gold  coin  per  Troy  ounce.  No  comparison,  however,  can 
now  be  made,  the  price  of  silver  being  variable.  The  value 

was  deduced  as  follows  : 

9 
$12.80  silver  coin =11  ounces  Troy,— of  this  gives  the 

12  80 
pure  metal =9. 9.  ounces.    -^r-= 1.2929  as  the  coin  value  of 


pure  silver. 


9.9 


142 


TABLES  AND   REFERENCES. 


OKES— CHARACTERISTICS. 

LEAD. 


ORES. 

COMPOSITION. 

COLOR. 

HARDNESS. 

SPECIFIC 
GRAVITY. 

SOLUBILITY. 
SOLVENTS. 

ON  CHARCOAL. 
BEFORE  THE 
BLOWPIPE. 

Galena. 

PbS 

Steel-gray. 

2.5-2.7 

7.2-7.7 

Nitric  acid. 

Gives  off  SO2 
and  fuses. 

Cerussite. 

PbC03 

Variable. 

3—3.5 

6.4 

Nitric  with 
effervescence. 

Cracks  and 
fuses. 

Anglesite. 

PbS04 

White 
tinged  with 
yellow,  etc. 

2.7-3 

6.2 

Insoluble. 

« 

Minium. 

Pb304 

Red  and 
yellow. 

3-4 

4.6 

Soluble. 

Lead 
Globules. 

Pyromor- 
phite. 

Pfe°lf2+ 

Green,  yel- 
low, brown, 
blue. 

3.5—4 

6.5—7 

Soluble. 

Fusible,  lead 
coat. 

ANTIMONY. 


Native. 

Sb 

Tin-  white. 

3—3.5 

6.7 

Hot 
muriatic. 

Fuses,  white 
fumes. 

Stibnite. 

Sb2S3 

Lead-gray 
to  blackish. 

2 

4.5—4.6 

Soluble. 

Fuses  easily 
and  gives  off 
white  fumes. 

Oxides. 

Sb2O3 
Sb2O6 

Variable. 

2-3 

5—5.5 

Muriatic  and 
aqua  regia. 

Fuse  and 
volatilize. 

SILVER. 

Native  silver 
and  alloys. 
Compounds 
With  S.As.Sb. 
Cl.Br.I.Te.Se 
etc. 

See  page  145. 

Variable. 

Variable. 

Variable. 

Nitric  acid 
and  aqua   re- 
gia. 

Give,  when 
fused  on  char- 
coal with  soda 
and  test  lead, 
and  the  but- 
ton cupelled,  a 
bead  of  silver. 

GOLD. 

Native  and  al- 
loys.   Com- 
pounds with 
Te  andSe. 

See  page  146. 

Generally 
yellow. 

2.5—3 

15—19 

Aqua  regia. 

Fusible  to  a 
bead,  better 
with  borax 
glass. 

PLATINUM. 

Native  and 
alloys. 

Pb.Ir.Au.Pd. 

etc. 

Whitish, 
blue  and 
gray. 

4-4.5 

16—19 

Aqua  regia. 

Infusible. 

OEES— CHAEACTEEISTICS. 
ZINC. 


143 


ORES. 

COMPOSITION. 

COLOR. 

HARDNESS. 

SPECIFIC 
GRAVITY. 

SOLUBILITY. 
SOLVENTS. 

ON  CHARCOAL. 
BEFORE  THE 
BLOWPIPE. 

Blende. 

ZnS 

Variable. 

3.5-4 

3.9—4 

Nitric,  and 
gives  off  IJ2S. 

Infusible. 
Reactica  for 
zinc. 

Smithsonite. 

ZnCOg 

White  to 
brown. 

5 

4—4.4 

Nitric  and 
other  sicids. 
Effervesces. 

Infusible. 
Reaction  for 
zinc. 

Calamine. 

Z%Sj04+ 

Variable. 

5 

3.3-3.5 

Gelatinizes. 

Fuses  with 
difficulty.  Re- 
action for  zinc 

Willemite. 

ZnSiO3 

Green, 
red,  yellow, 
gray. 

5.5 

3.8-4 

Muriatic  acid. 

Fusible  with 
difficulty. 
Zinc  coat. 

Zincite. 

ZnO 

Red. 

4-4.5 

5.4—5.8 

All  acids. 

Infusible. 
Reaction  for 
zinc. 

MERCURY. 


Mercury.               Hg 

Tin-white. 

-1 

13.5 

Nitric  acid. 

Volatile. 

Cinnabar.     ;         HgSa 

Red. 

£—2.5 

8.9 

Aqua  regia. 

Volatile,gives 
fumes  S02 

Calomel. 

HgaCla 

White    to  !        1     o 
brown.    | 

6.4 

Aqua  regia. 

A^olatile. 
White  coat. 

BISMUTH. 

Native. 
Oxide.        I 
Sulphide,   j- 
Arsenide.  J 

Bi-S-As 

Sometimes 
with  C  u.  Pb. 
etc. 

Reddish  to 
white. 

Variable 
when  com- 
bined. 

When  pure 
metal. 
2—2.5 

Variable. 

When  pure 
metal. 
9.7 

Variable. 

Nitric  and 
muriatic 

acids. 

Easily  fusible. 

Volatile,  giv 
ing  orange- 
yellow  coat. 

TIN. 

Cassiterite. 

SnO2 

STariable. 

6—7 

6.3—7.1 

Insoluble. 

Infusible. 
Reaction  for 
tin. 

Stannite. 

Cu2S  I  ~   o 
FeS     [SnS- 

Steel  gray 
to  black. 

4 

4.3-4.5 

Aqua  regia. 

Gives  fumes 
of  sulphurous 
acid  and  fuses 

COPPER. 

Native  and  al- 
loys, oxidized 
ores  and  com- 
pounds, with 
S.As.Sb.,  etc. 

See  page    91. 

Variable. 

2-4.5 

Native,  8.9  ; 
ores,  4—6. 

Nitric  acid. 

Fusible  or  re- 
ducible 10  me- 
tal, reaction 
for  copper. 

144 


TABLES  AND   REFERENCES. 
IRON. 


ORBS. 

COMPOSITION. 

COLOR. 

HARDNESS. 

SPECIFIC   - 
GRAVITY. 

SOLUBILITY. 
SOLVENTS. 

ON  CHARCOAL, 
BEFORE  THE 
BLOWPIPE. 

Magnetite. 

FesO< 

Black,  mag- 
netic. 

5.5—6.5 

4.9—5.1 

Muriatic  and 
aqua  regia. 

Infusible. 

Hematite. 

Fe203 

Red  to 
black. 

5—6.5 

4.5—5.3 

Muriatic  and 
aqua  regia. 

Infusible,  be- 
come? mag- 
netic. 

Limonite. 

W 

Dark- 
brown. 

5—5.5 

3.6—4 

Muriatic, 
warm. 

Infusible,   be- 
comes mag- 
netic. 

Siderite. 

FeC03 

Variable. 

3.5-4.5 

3.7—3.9 

Soluble  with 
effervescence 
in  hot  acids. 

Infusible,  be- 
comes mag- 
netic. 

Ilmenite. 

FeTiO3+ 
nFe2O3 

Iron-black, 
slightly 
magnetic. 

5—6 

4.5—5 

Aqua  regia. 

Infusible. 

Franklinite. 

(FeO.ZnO. 

MnO).(FeQO3 
Mn203) 

Black. 

5.5—6.5 

4.8-5.1 

Warm  muri- 
atic. 

Infusible, 
reaction  for 
zinc. 

Pyrite. 

FeS2 

Yellow. 

6—6.5 

4.8—5 

Nitric  acid. 

Gives  off  SO, 
and  becomes 
magnetic. 
Fuses. 

Pyrrhotite. 

Fe7S8 

Yellow  to 
red. 

3.5—  4.5 

4.5 

Nitric  acid. 

Magnetic 
Globules. 

Chromite. 

FeCr2O4 

Black. 

5.5 

4.3-4.6 

Insoluble. 

Infusible. 

MANGANESE. 


Oxidized  ores. 

See  page  138. 

Dark-brown 
to  black. 

1-6 

8-5 

Cone,  muri- 
atic :  gives  off 
Cl. 

Infusible. 
Reaction  for 
manganese. 

NICKEL  AND  COBALT. 

Niccolite. 

NiAs 

Copper-red. 

5—5.5 

7.3—7.6 

Aqua  regia. 
Green  solu- 
tion. 

Fuses  with 
odor  of  As. 
Reaction  for 
Ni. 

Millerite. 

NiS 

Brass  or 
bronze-yel- 
low. 

3—3.5 

4.6—5.6 

Aqua  regia. 

Fuses  to  a 
brittle  mag- 
netic globule. 
Reaction  for 

Ni. 

Smaltite. 

(Co,Ni)Asa 

Tin-white 
to  gray. 

5.5-6 

6.4-7.2 

Nitric  acid. 
Pink  sol. 

Gives  off  As, 
melts,  and  re- 
action for  Co. 

Cobaltite. 

CoS2+CoAs2 

Silver-white 
to  gray. 

5.5 

6-6.3 

Nitric  acid. 

Gives  off  As, 
and  becomes 
magnetic. 

Linnaeite. 

Co3S4 

Yellow. 

5.5 

4.8—5 

Nitric  acid. 

Fusible. 
Reaction  for 
cobalt. 

ORES — CHARACTERISTICS. 
CARBON. 


145 


Diamond, 

Graphite, 

Coals,  Lignite 

and  Wood. 


Sulphur 

and 
Sulphides. 


COMPOSITION. 


Pure  to  vari- 
able. 


Variable. 


Colorless  to 
black. 


Variable. 


SPECIFIC 
GRAVITY. 


Variable. 


SOLUBILITY. 
SOLVENTS. 


SULPHUR. 


Yellow, 
when  pure. 


Variable. 


Variable. 


Insoluble. 


When  pure, 

in  bi-sulphide 

of  carbon. 


ON  CHARCOAL, 
BEFORE  THE 
BLOWPIPE. 

Burn,  leaving 
an  ash,  MI..J 
in  the  case  of 
the  diamond. 


Melt   and 


most  cases. 


SILVER — ORES   AND   MINERALS. 


MINERAL. 


COMPOSITION. 


PER  CENT.  OF  SILVER, 
WHEN  PURE. 


Naumannite . .  Ag^Se 73.2 

Eucairite Cu2Se  + Ag.Se 43.1 

Hessite Ag2Te 62.8 

Petzite (Au,Ag)8Te 41.8 

Sylvanite (Au,Ag)Te3 10.— 15. 

Silver  Glance.  Ag2S 87.1 

Stromeyerite. .  Ag2S  +  Cu2S 53.1 

Sternbergite. .  AgFe2S2 34.2 

Miargyrite  . . .  Ag2S  +  Sb2S3 36.7 

Pyrargyrite  .  .3Ag2S  +  Sb2S3 59.8 

Proustite 3Ag2S  +  As2S3 65. 4 

Stephanite  ...  5Ag2S  +  Sb2S3 68. 5 

Brogniardite. .  PbS  +  Ag2S  +  Sb2S3 26.1 

Polybasite . . .  .9(Ag2Cu)S  +  (Sb, As)2S3 68. 

Tetrahedrite  j  (Cu,Ag)2S  +  (Sb,As,Bi)2S3+  ) 
(FaMerz)     |  (Fe,Zn,Hg)S  \  "" 

Xanthoconite .  (3  Ag2S,  As2S5)  +  2(3  Ag2S,  AS2S3) 64. 

Fireblende. . . .Ag-Sb— S 62.3 

Freieslebenite.Pb2Ag3Sb3S8 23.8 

Cerargyrite. .  . AgCl 75.33 

Bromyrite ....  AgBr 57.4 


140  TABLES   AND   EEFEEENCES. 

Embolite  ......  Ag(Cl,Br)  ...........  .............  61.—  71 

lodyrite  ......  Agl.  .............................  46. 

Minerals  often  containing  silver  in  small  quantities  : 
Galena  ........................  PbS. 

Blende  ........................  ZnS. 

Pyrite  .........................  FeS2. 

Chalcopyrite  ..................  CuFeS2. 

Erubescite  .....................  Cu3FeS8. 

Mispickel  .........  ,  ...........  FeS2  +  FeAs2. 

Altaite  .......................  PbTe. 

Clausthalite  ...................  PbSe. 

Nagyagite  .....................  (Pb,  Au,  Ag)(Te,S)2. 

Chiviatite  .....................  (Cu2Pb)S.|Bi2S3. 

Pufrenoysite  ..................  PbS  +  As2S3. 

Enargite  ......................  3Cu2S  +  As2S3. 

Slags,  etc. 

Cupel  Bottoms,  Dross,  Litharge,  Sweeps,  etc. 

SILVEE  —  ALLOYS. 


Native  Silver  ...................  AgAu  (generally) 

Native  Gold  ....................  AuAg  ...........  1.—  35. 

Native  Copper  ..................  CuAg  .......  sometimes  10 

Chilenite  .......................  Ag12Bi  ...........      86.2 

Bismuth  Silver  .................  Ag—  Cu—  As—  Bi      60. 

Dy  scrasite,  Antimonial  Silver  .  .  .  Ag4Sb  ...........      78. 

Amalgam  .....................  AgHg  ...........      35. 

......................  Ag2Hg3  ..........      26. 

Arquerite  .......................  Ag12Hg  ..........      86.5 

Artificial  Alloys,  Silver  Coin,  Jewelry,  etc. 

GOLD  —  MLNEEALS. 

Sylvanite—  Graphic  Tellurium  (Au,  Ag)Te8—  Au  28.—  Ag  15. 
Calverite  ................................  AuTe4  —  Au  44. 

Nagyagite-Foliated  Tel-  (  (Fb,Au  i^Ag)  )      .Au9._Ag0.5. 
lurmm  1    (Te,Sb,S)    ) 


OEES — CHARACTERISTICS. 


147 


GOLD — ALLOTS. 

Native  Gold AuAg— Au  65. — 99. 

Palladium  Gold— Porpezite..AuPd— Au  85.98— Ag  4.17. 

Rhodium  Gold AuRd— Au  59.— 66. 

Gold  Amalgam (Au,Ag)4Hg5— Au38.39— Ag5. 

Artificial  Alloys,  Gold  Coin,  Jewelry,  etc. 

The  preceding  list  does  not  include  all  of  the  rare  min- 
erals of  gold  and  silver  ;  for  these  the  reader  is  referred  to 
Dana' s  System  of  Mineralogy. 


WEIGHT   OF   ONE  CUBIC   FOOT,    AND  VOLUME   OF   ONE  TON, 
OF   SOME  IMPORTANT   MINERALS. 


(1  cubic  foot  of  water=62.4  Ibs). 


MINERAL. 

WEIGHT 
OF  CUBIC 
FOOT. 

CUBIC 
FEET  IN 
ONE  TON. 

MINERAL. 

WEIGHT 
OF  CUBIC 
FOOT. 

CUBIC 
FEET  IN 
ONE  T0¥. 

Quartz     

162  Ibs. 

12.34 

Chalcopyrite  

262  Ibs. 

7.63 

Argentite 

455   " 

439 

(Copper  Pyrites.) 

(Silver  Glance  ) 

Tetrahedrite     .  . 

280  " 

714 

Pvrarsrvrite 

362   " 

5  52 

(Gray  Copper.) 

(Ruby  Silver  ) 

Galenite 

461   " 

4  34 

Proustite  

336   " 

5.95 

(Galena.) 

(Light  Ruby  Silver.) 

Sphalerite  

249   " 

8.03 

Stephanite  

386   " 

5.18 

(Blende.) 

(Black  Silver.) 

Pyrite  

312   " 

6.41 

Cerargyrite  

345    " 

5.80 

(Iron  Pyrites.) 

(Horn  Silver.) 

Limestone    

174  " 

11  50 

Stibnite 

287   " 

6  99 

(Calcite.) 
(Dolomite  ) 

(Antimony  Glance.) 

Kaolin  

162   " 

12.34 

Cinnabar  

549   " 

3.64 

(Clay.  ) 

NOTE.  —  The  values  given  above  are  for  the  pure  minerals,  and  can  be  ob- 
tained by  multiplying  the  weight  of  one  cubic  f«~*  il  water  by  the  specific 
gravity  of  the  mineral  ;  the  product=the  weight  of  a  cubic  foot  of  the  min- 
eral or  ore  ;  2000  divided  by  this  =  volume  of  one  ton^Y 


OF  THE 


E 

(TFNIVERSITY; 

\ 


148 


TABLES   AND   REFERENCES. 


COINS  OF   THE  UNITED  STATES. 

(By  Act  of  Congress,  February  12,  1873.) 
GOLD    COINS. 


DENOMINATION. 

WEIGHT. 

FINENESS. 

Dollar,  unit  of  value 
Quarter  Eagle,  $2.  50 
Three  dollars 
Half  Eagle,  $5 

Eagle,  $10 
Double  Eagle,  $20 

25.8  grains. 
64.5       " 
77.4       " 
129.0       " 
258.0       " 
516.0       " 

900. 

a 

a 

a 
a 
a 

SILVER    COINS. 

Dollar, 
Half  Dollar,  50c. 
Quarter  "      25c. 
Dime,             lOc. 

412?y  grains. 
192"       " 
96 
38.4      " 

900. 

a 

a 

a 

MINOR   COINS. 

Five  cent  piece 
Three  "       " 
One      "       " 

77.16  grains 
32.0 

48. 

Cu  75^,  Ni  25^ 
tt      tt      a     a 

Cu  95^,  Sn  and  Zi 
5*,  (3%  Sn,  2^  Zn 

MEASUKES  OF  WEIGHT  AND  VOLUME. 

AVOIRDUPOIS   WEIGHT. 

Used  for  weighing  base  metals,  as  lead,  antimony,  tin,  etc. 

15  Drams  (dr.) make  1  ounce, marked  oz. 

16  Ounces make  1  pound "        Ib. 

25  Pounds make  1  quarter, "        qr. 

4  Quarters make  1  hundred- weight  "      cwt. 

20  Hundred- weight make  1  ton "          t. 

TROY   WEIGHT. 

Used  for  weighing  precious  metals,  as  gold,  silver,  etc. 

24  Grains  (gr) make  1  pennyweight. . .  "    dwt. 

20  Pennyweights make  1  ounce "        oz. 

12  Ounces make  1  pound "        Ib 


MEASUEES    OF   WEIGHT   AND   VOLUME.  149 

FEENCH   OE  DECIMAL   WEIGHTS. 

Used  in  weighing  all  metals. 

10  Milligrammes  (mg.)  .  .make  1  centigramme. .  marked  c£,. 

10  Centigrammes make  1  decigramme. . .       "     dcg. 

10  Decigrammes make  1  gramme ,       "      gm. 

10  Grammes make  1  decagramme  ..        "     dkg. 

10  Decagrammes make  1  hectogramme  .       "       hg. 

10  Hectogrammes make  1  kilogramme. . .        "       kg. 

10  Kilogrammes make  1  myriagramme.       "  myrg. 

The  unit  of  the  system  is  the  gramme =15. 432349  Troy 
grains,  or  the  weight  of  1  c.c.  distilled  water  at  60°  F. 

ASSAY   WEIGHTS. 

(4  Assay  Tons=116. 66666  grammes. 

MultlPleS )  2  Assay  Tons=  58.33333  « 

Unit. .  .The  Assay  Ton  (marked  A.  T.)=  29.16666  " 

1-3    Assay  Ton=     9.7222  " 

1-6        "         "-  =     4.8611  " 

1-10      "         "    =     2.9166  " 
1-20      "         "    =     1.4583 

LIQUID   MEASUEE. — UNITED   STATES. 

4  Gills  (gi. ) make  1  pint marked  pt. 

2  Pints .make  1  quart "       qt. 

4  Quarts make  1  gallon "      gal. 

LIQUID    MEASUEE. — FEENCH. 

10  Milliliters  (ml.) make  1  centiliter marked  cl. 

10  Centiliters make  1  deciliter "     del. 

10  Deciliters make  1  liter "        1. 

10  Liters make  1  decaliter "    dkl. 

10  Decaliters make  1  hectoliter "      hi. 

10  Hectoliters make  1  kiloliter "     kl. 

The  unit  is  1  liter =61. 027052   cubic  inches,  or  1.760773 
pints. 


150  MEASURES   OF  WEIGHT  AND  VOLUME. 

CUBIC   MEASURE. — ENGLISH. 

1728  Cubic  inches  (c.  in.)  make  1  cubic  foot,  marked  cu.  ft. 

27  Cubic  feet make  1  cubic  yard  c.  yd. 

16  Cubic 'feet make  1  cord  foot..  c.  ft. 

8  Cord  ft.or!28  cubic  ft.make  1  cord "  c. 

CUBIC  MEASURE. — FRENCH. 

1000  Cubic  centimeters  (c.  c.)  make  one  cubic  decimeter  or 

litre,  marked  1. 
1000  Cubic   decimeters   make   1    cubic   meter   or  kiloliter, 

marked  kl.  or  cu.  m. 
Otherwise  the  cubic  measure  is  the  same  as  liquid. 

COMPARISON    OF   UNITS. 

1  Meter =39.37079  inches. 

1  Are =  (393. 7079)2= 155005. 91  sq.  inches. 

1  Liter =  (3. 937079)°= 61. 027  cubic  inches. 

1  Pound  Avoirdupois. ..=7000  grains  Troy. 

1  Pint,  U.  S =28.875  cubic  inches. 

1  English  ton  (2240  lbs.)=15,680,000  grains. 
1  Short  ton  (2000  Ibs.). .  =14,000,000  grains. 


SPECIFIC  GRAVITY. 

The  specific  gravity  of  a  body  is  the  weight  of  that  body 
as  compared  with  the  weight  of  an  equal  volume  of  another 
body,  assumed  as  a  standard. 

The  standard  for  solids  and  liquids  is  distilled  water ; 
for  gases  and  vapors,  dry  air  and  sometimes  hydrogen. 


SPECIFIC   GEAVITY.  151 

All  determinations  must  be  made  at  known  temperatures  ; 
this  for  solids  and  liquids  is  60°  F. 

Gases  and  vapors  may  be  observed  at  any  known  temper- 
ature, and  the  volume  reduced  by  calculation  to  what  it 
would  be  at  60°  F. 

Formulae  for  the  determination  of  the  specific  gravity  of 
solids  and  liquids : 

a.     Solids. 

1.  The  substance  is  heavier  than  water,  and  insoluble  in 
it.     Weigh  it  in  air  and  then  in  water  : 

Let  the  weight  of  the  substance  in  air^W. 

Let  the  weight  of  the  substance  in  water  =W. 

W 

The  specific  gravity=w_w/ 

2.  The  substance  is  heavier  than  water  and  insoluble 
in  it : 

Fill  a  flask  to  any  fixed  mark  on  the  neck,  with  water, 
and  weigh  ;  the  weight —W.  W= weight  of  the  substance. 
Place  it  in  the  flask  and  reduce  the  water  to  the  same  level, 
then  weigh  the  flask,  plus  substance  and  water  left.  Let 

this  weight= W". 

W 

The  specific  gravity = 


3.  The  substance  is  heavier  than  water,  but  in  fragments, 
and  is  insoluble.     Use  the  same  method  as  in  2. 

4.  The  substance  is  heavier  than  water,  but  soluble  in  it: 
Weigh  in  some  liquid  of  known  specific  gravity  in  which 

it  is  insoluble,  in  place  of  water.     Calculate  as  follows  : 
Weight  of  substance  in  air=W. 
Weight  of  substance  in  liquid =W. 
Specific  gravity  of  liquid=S. 
Specific  gravity  of  water =1. 


152  TABLES   AKD   REFERENCES. 

,  The  liquid  displaced  =  W—  W'=X. 
Then  S  is  to  1  as  X  is  to  W'^the  water  that  would  have 

been  displaced. 

W 

The  specific  gravity  =  - 


5.     The  substance  is  insoluble,  but  lighter  than  water  : 
'   Weight  of  the  substance  in  air—  W. 

Then  weigh  in  water  with  a  piece  of  lead  attached  to 
sink  it.     Let  this—W'. 

Weight  of  the  lead  alone  in  water  ^W* 

W 

The  specific  gravity^: 


6.  The  substance  is  soluble,  but  lighter  than  water. 

Use  the  process  by  the  flask  as  in  2,  but  substitute  ben- 
zine or  turpentine  for  water. 

Weight  in  air  ==  W  ;  in  liquid  =  W'  .  Specific  gravity 
of  liquid  =  S.  Water  =  1.  W-  W=  W*  -  liquid  dis- 

placed.     S  is  to  1  as  W"  is  to  X  =  the  water  that  would 

W 

have  been  displaced.     Specific  gravity  =  -^ 

b.  Liquids. 

Three  methods  may  be  employed. 

1.  By  the  specific  gravity  bottle.     This  is  a  thin  glass 
flask  with  a  hollow  stopper,  so  as  to  allow  the  insertion  of 
a  thermometer. 

Weight  of  the  flask  =  W. 

filled  with  water  =  W'. 

"    the  liquid  =  W". 
W"-W 
Specific  gravity  =  =  -^ziw 

2.  By  weighing  some  body  first  in  water  and  then  in  the 
liquid. 

The  body  weighed  in  air=W. 
"  "      water=  W7. 

"      liquid-W". 

.,  W"-W 

Specific  gravity  =         r 


THEEMOMETEES.  153 

3.  By  means  of  the  hydrometer,  which  is  an  instrument 
that,  placed  in  a  liquid,  shows  its  specific  gravity  by  direct 
inspection.  Its  action  depends  upon  the  simple  principle 
that  a  floating  body  displaces  its  own  weight  of  liquid. 
Hydrometers  vary  in  construction  according  to  the  pur- 
poses for  which  they  are  to  be  used,  but  are  generally  made 
of  light  glass  tubes  with  bulbs,  blown  in  a  single  piece  ;  the 
weight  desired  being  given  by  means  of  small  shot  or  mer- 
cury placed  in  the  bulb  at  the  lower  end,  which  is  after- 
wards carefully  sealed. 

The  graduation  may  be  made  according  to  the  true  scale 
of  specific  gravities  or  arbitrarily  ;  the  first  is,  of  course, 
most  desirable  and  generally  employed.  For  commercial 
purposes  the  Baume  scale  is  often  used  ;  it  is  arbitrary,  and 
is  determined  by  marking  the  point  to  which  the  instrument 
sinks  in  pure  water  "0,"  and  the  point  to  which  it  sinks  in 
a  solution  of  15  parts  of  salt  in  85  of  water,  "15,"  the  inter- 
val being  divided  into  15  equal  parts.  For  specific  gravity 
of  gases  and  vapors,  see  Watts'  Dictionary  of  Chemistry, 
Vol.  V.,  page  360. 

THERMOMETERS. 

Three  scales  are  now  in  general  use.     These  are  : 

1.  Centigrade—  C.     Water  freezes  at    0°,  boils  at  100°. 

2.  Fahrenheit—  F.         "  "       32°,        "       212°. 

3.  Reaumur—  R.  "  "         0°,        "         80°. 


To  CONVEET—  F.  to  0 


90. 


C.  to  F.   ~  +32°=F. 
5 

QT?  ° 

R.toF.   y-^ 


>  Formulae. 


154  TABLES  AND   KEFEKENCES. 

TABLE  OF  VALUES  FOR  GRAIN  WEIGHTS. 


sg>s 

5-0 

O 

sg>s 

g-0 

O 

2. 

5§>S 

5-o 

g 

TO  ^  Jf 

1-3  CD 

p' 

OQ  CD   g 

ngfc 

QT5  CD   JfO 

k^CD 

(o  z£  O 

o  H 

j 

p   &  O 

o  "~3 

^ 

P    ^ 

0  ^ 

A 

S"  ^  dQ 

•3  o 

M 

3*  ^  T3 

*<  o 

^< 

C*  CtJ  QTQ 

•§   0 

*S 

QD    p    *"* 

To' 

|a 

pT 

CD 

r!'  i 

o  ^ 

s  o 

3   ,-K 

CD 

QG    50^3 

c  3 

P? 

o> 

fa 

1 

Is, 

So 

1 

i        £r° 

CD  0 

1 

§  o 
II 

i"a 

o 
o 

§  o 

II 

•  3 

i  a 

O 
3 

|| 

:^ 

o 

•  «<j 

1 

Q 

tr  < 

:  c 

\ 

?i' 

:  CT 

1 

CD  CD 

0, 

00  CD 

rh* 

o 

S    CK 

I-I. 

Q 

aa 

i  1 

p, 

':  2,2, 

:  S 

s 

2,2, 

i  S 

P 

.001 

1.21 

$  25.11 

r 

44.95 

$  929.19 

3 

88.69 

$  1,883.37 

2 

2.43 

50.23 

8 

46.17 

954.42 

4 

89.91 

1,858.59 

3 

3.64 

75.24 

9 

47.38 

979.43 

5 

91.12 

1  883  .  60 

4 

4.86 

100.46 

.040 

48.60 

1,004.65 

6 

92.34 

1.908  .  82 

5 

6.07 

125.48 

1 

49.81 

1,029.66 

7 

93.55 

1,933.83 

6 

7.29 

150.70 

2 

51.03 

1,054.88 

8 

94.77 

1,959.05 

7 

8.50 

175.71 

3 

52.24 

1,079.89 

9 

95.98 

1,984.06 

8 

9.72 

200.93 

4 

53.46 

1.105.11 

.080 

97.  2J 

2,009  .  28 

9 

10.93 

325.94 

5 

54.67 

1,130.12 

1 

98.41 

2,034  .  29 

.010 

12.15 

251  .  16 

6 

55.89 

1,155.34 

2 

99.63 

2,059  .  51 

1 

13.39 

276.17 

7 

57.10 

1,180.35 

3 

100.84 

2,084  .  52 

2 

14.58 

301.39 

8 

58.32 

1.205.57 

4 

102.06 

2,109  .  74 

3 

15.79 

326.41 

9 

59.53 

1,230.58 

5 

103.27 

2.134.75 

4 

17.01 

351.63 

.050 

60.75 

1,255.80 

6 

104.49 

2.159.97 

5 

18.22 

376.64 

1 

61.96 

1,280.81 

7 

105.70 

2,184.98 

6 

19.43 

401.65 

2 

63.18 

1,306.03 

8 

106.92 

2,210.20 

7 

20.65 

426.87 

3 

64.39 

1,331.04 

9 

108.13 

2,235  .  21 

8 

21.86 

451.88 

4 

65.61 

1,356.26 

.090 

109.35 

2,260  .  43 

9 

23.08 

477.10 

5 

66.82 

1,381.27 

1 

110.56 

2,285  .  44 

.020 

24.30 

502.32 

6 

68.04 

1,406.49 

2 

111.78 

2,310.66 

1 

35.51 

527.34 

7 

69.25 

1,431.50 

3 

112.99 

2,335  .  67 

2 

26.73 

552.56 

8 

70.47 

1,456.72 

4 

114.21 

2,360  .  89 

3 

27.94 

577.57 

9 

71.68 

1,481.73 

5 

115.42 

2,385  .  90 

4 

29.16 

602.79 

.060 

72.90 

1,506.95 

6 

116.64 

2,411.12 

5 

30.37 

627.80 

1 

74.11 

1,531.96 

7 

117.85 

2,436.13 

6 

31.59 

653.02 

2 

75.33 

1,557.18 

8 

119.07 

2,461.35 

7 

32.80 

678.  0? 

3 

76.54 

1,582.19 

9 

120.28 

I     2,486.36 

8 

34.02 

703.25 

4 

77.76 

1,607.41 

.100 

121.50 

2,511.62 

9 

35.23 

728.26 

5 

78.97 

1,632.42 

.200 

243.00 

5,023.25 

.030 

36.45 

753.48 

6 

80.19 

1,657.64 

.300 

364.50 

7,131.77 

1 

37.66 

778.50 

7 

81.40 

1,682.65 

.400 

486.00 

10,046.50 

2 

38.88 

803.72 

8 

82.62 

1,707.87 

.500 

607.50 

15,558.12 

3 

40.09 

828.73 

9 

83.83 

1,732.88 

.600 

729.00 

14.263.55 

4 

41.31 

853.95 

.070 

85.05 

1,758.13 

.700 

850.50 

17,581.37 

5 

42.52 

878.96 

1 

86.26 

i   1,783.14 

.800 

972.00 

20,093.00 

6 

43.74 

904.18 

2 

87.48 

1,808.36 

.900 

1,093.50 

22,604.61 

1000 

1,215.00 

25,116.25 

MULTIPLICATION  TABLE  FOR  GOLD. 


20.67X1=20.67 
20.67X2=41.34 
20.67X3=62.01 


20.67X4=  82.68  20.67x7=144.69 

20.67X5=103.35  20.67x8=165.36 

20.67X6=124.02  20.67x9=186.03 

I  $4134. 
206.7 
165  36 
1^402  added  will  give 
$4518.462  per  ton  of  2000  Ibs. 


GENERAL   STYLE   OF   REPORT. 


155 


PROPORTIONS  OF  LEAD  FOR  CUPELLING  GOLD 
ALLOYS  (KAKDELHARDT). 

GOLD  IN   1000  PARTS.  QUANTITY  OP  LEAD  REQUIRED. 

1000  fine  gold 8  times  the  weight  of  the  alloy. 

980-920 12  " 

920-875 16  " 

875-750 20  " 

750-600 24  " 

600-350 28  " 

350-  0  32  " 

GENERAL  STYLE  OF  REPORT. 

(Certificate.) 

New  York, 18 

DEAR  SIR  : 

The  sample  of 

From _ 

Marked 

submitted  to  me  for  examination,  contains : 


Very  respectfully, 


To 


156  TABLES   A1STD  REFERENCES. 

QUANTITATIVE  REPORT. 

(.For  Keference.) 


New  York, 18 


Report  of 
Analysis  of 

Determination  of 
Weight  taken 
Method  of  Analysis. 


Actual  Calculated  Theoretical 

Precipitates.          Weights.          Cor  stituents.          Weights.          Percentages.         Percentages- 


Remarks 


BLANK   EEPOETS. 


157 


Remarks. 

True 
PerCent. 

BUTTON. 

Average 
PerCent. 

PerCent. 

"3 

Character. 

d 

OQ 

1 

o 

'o 

EH 

Total. 

' 

After 
Fusion. 

oj 

•8* 
o'l 

1 

4 

O    OB 

158 


TABLES   AND   REFERENCES. 


IRON— CRUCIBLE  ASSAY. 


Ore  —  Marked 

Mineral  Character 

Composition 

Alumina               per  cent. 

Silica 

Lime 

No.  1. 

No.  2.       i 

Charge  —  Ore 

Gms. 

Gms. 

Silica 

tt 

u 

Lime 

« 

it 

Glass 

it 

ii 

Kaolin 

it 

a 

Fluorspar 

tt 

a 

In  fire  — 
Slag,  Color 
Appearance 
Button,  Wt. 

Hours. 

Hours. 

Gms. 

Gms. 

Character 

Remarks 


REPORT. 


Assay 
No.  1 

No.  2 

Average 

Sample  Averaged  on 
Dated 

No. 


per  cent  Iron. 


u         tt        u 

Ibs.  Ore 


Signed 


UNIVERSITY) 


BLANK   REPORTS. 


SILVER  AND  GOLD— CRUCIBLE  ASSAY. 


159 


Ore — Marked 

Mineral  Character 
Reducing  Power 

Charge — Ore 

Litharge 

Garb.  Potash  or  Soda 
Borax  Glass 
Silica 

Charcoal  or  Argol 
Nitre 
Salt 
In  fire — to  fusion 

after  fusion 
Slag,  Color 

Appearance 
Lead  Button,  Wt. 

Character 
Scorification — Fluxes 

Wt.  after  1st. 
"   2nd. 

Cupellation — Silver  and  Gold 
Gold  in  Ore 
Silver 

Silver  in  Litharge 
Silver  in  Ore 

Remarks 


Gms. 


Gms.  Lead. 


No.  1. 

No.  2. 

A.  T. 

A.  T. 

(c 

« 

Gms. 

Gms. 

Mts. 

«  c 

Mts. 

Gms. 

Gms. 

Gms. 

Gms. 

" 

<  i 

Mgs. 

Mgs. 

c  < 

1  1 

<  t 

" 

REPORT. 

Contained  in  2,000  ft>s.  Ore 


Assay 
No.  1. 

Gold 
oz. 

Silver 
oz. 

Total 
oz. 

Gold 

$5 

Silver 

Total 

No.  2. 
Average 

oz. 

oz. 

oz. 

$ 

$ 

1 

oz. 

oz. 

oz. 

$ 

$ 

$ 

Sample  Averaged  on                              Ore 

Dated 
No. 


Signed 


160 


TABLES   AND   REFERENCES. 


SILVER  AND  GOLD— SCORIFICATION  ASSAY. 

Ore — Marked 

Mineral  Character 


Charge — Ore 

Test  Lead 
Borax  Glass 
Silica  or  Glass 
No.  of  Scorifiers 
Scorification 
Slag— Color 

Appearance 
Button — Character 
Weight 

"      after  2nd  Scor. 
"          "    3rd    " 
"    4th   " 
"     5th    " 
Cupellation 

Gold  in  Ore 
Silver 

Silver  in  Test  Lead 
Silver  in  Ore 

Eemarks 


No.  1. 

No.  2.          » 

A.  T. 

A.  T. 

Gms. 

Gms. 

Gms. 

Gms. 

<  i 

« 

Mgs. 

Mgs. 

« 

« 

" 

" 

REPORT. 


Contained  in  2,000  ft>s.  Ore. 


Assay- 

Gold 

Silver 

Total 

Gold 

Silver 

Total 

No.  1. 

oz. 

oz. 

oz. 

$ 

$ 

$ 

No.  2. 

oz. 

oz. 

oz. 

$ 

$ 

$ 

Average 

oz. 

oz. 

oz. 

8          I  8 

$ 

Sample  Averaged  on                               Ore 

Dated 

No.                                                           Signed 

BLANK   EEPOETS. 


GOLD  BULLION  ASSAY. 


161 


Alloy — Marked 


Copper  Assay 
Bullion 
Lead 
Gold  and  Silver 
Base  metal 

Assay  proper 
Cupellation 
Bullion 
Silver 
Lead 
Copper 

Parting 
Cornet 
Silver  retained 
Gold 

No.  1. 

Mgs. 
Gins. 
Mgs. 

a 

No.  2. 

Mgs. 
Gms. 

Mgs. 

a 

Mgs. 

« 

Gms. 

a 

Mgs. 

a 

Gms. 

a 

Mgs. 

u 

Mgs. 
a 

u 

a 

Remarks 


EEPOET. 


Assay 
No.  1. 
No.  2. 
Average 

Dated 
No. 


Gold. 

Silver. 

Base  Metal. 

Fine 

Thds. 

Thds. 

a 

u 

u 

u 

u 

u 

Signed 


162  TABLES   AND   KEFEKENCES. 

SILVER  BULLION  ASSAY. 
Alloy — Marked 


Cupellation 
Bullion 
Lead 
Silver 

Correction  for  Loss 
Fineness 

Volumetric  Assay 
Bullion 

Normal  Salt  solution 
Decimal     "        " 

Total 
Decimal  Silver  solution 

Total  Salt 
Equivalent  in  Silver 

Fineness 

Kemarks 


No.  1. 


Mgs. 
Gms. 

Mgs. 


Gms. 
100.  c.c. 


Gms. 
Thds. 


No- 


Mgs. 
Gms. 

Mgs. 


Gms. 
100.  c.c. 


Gms. 
Thds. 


Assay 

No.  1. 
No.  2. 


Average 
Dated 


No. 


EEPOET. 

Silver. 


Copper,  &c 


Fine. 


Thds. 


Signed 


PROBLEMS  AND   QUESTIONS.  163 

PROBLEMS  AND  QUESTIONS. 

1 .  What  would  be  the  best  method  of  assaying  a  poor 
argentiferous  sulphide  of  antimony  for  the  silver  ? 

2.  Explain  the  derivation  of  the  assay  ton,  and  calculate 
its  weight  for  England  and  the  United  States. 

3.  An  iron  ore  contains  by  analysis — 
Silica 6.61  per  cent. 


Alumina. .     .  .0.55 


Calculate  the  charge  for 
Percy's  slag. 


Lime 4.68 

Magnesia 1.37       " 

Answer : 

Silica 0.894 

Kaolin 1.890 

Lime 2.395 

4.  What  is  the  theory  of  the  lead  assay  ? 

5.  Describe  the  operations,  and  the  theory  of  the  scorifi- 
cation  assay  for  silver  ores. 

6.  What  would  be  the  best  method  of  treating  a  pure 
iron  pyrites  containing  gold  ? 

7.  Mention  the  reagents  employed  in  the  crucible  assay 
of  silver  ores,  and  the  action  of  each. 

8.  Given  an  ore  containing,  gold  0.0925  grains  in  6  Troy 
oz.;  silver,  0.046  grains  in  6  Troy  oz.;  which  has  a  reducing 
power  of  2=14  of  lead.    Calculate  the  best  charge  for  assay, 
and  give  the  value  in  ounces  per  ton. 

Answer  :     Roast.     Charge  of  ore,  4  A.  T. 

Silver 0.466  oz. 

Gold 0.936  " 

9.  50  gms.  of  an  ore,  sifted,  gave  2.59  scales  and  47.40 
gins,  siftings.     The  scales,  melted  down  with  lead,  gave  a 
button  of  35  gms.     10  gms.  of  this  button  yielded,  silver 


164  TABLES   AND   REFEKENCES. 

4.5  mgs.  ;  gold  1.3  mgs.  J  A.  T.  of  the  sif  tings  yielded 
silver  6.95  mgs.  ;  gold  1.85  mgs.  Required  the  value  of 
the  original  ore  in  ounces  per  ton. 

Answer  : 

Silver  ...............................  28.96  oz. 

Gold  ................................  7.92  " 

10.  An  alloy  cupelled,  gave  0.9848  gms.  of  silver  in  one 
gramme.     Added  in  the  volumetric  test  :     Normal  salt,  100 
c.c.  ;  decime  salt,  5  c.c.  ;    decime  silver,  2  c.c.  :  99.7  c.c. 
normal  salt—  1  gm.  of  pure  silver.     Calculate  the  weight  of 
the  alloy  taken  for  volumetric  assay,  and  the  fineness. 

Answer  : 

Weight  taken  for  assay  =1.01  54  gms. 
Fineness  .....................  994.71. 

11.  Calculate  the   charges  for  the  following  reducing 
powers,  the  charge  of  ore  being  one  assay  ton  :     (2  gms.  = 
16.5),  (2  gms.  =0.42),  (2  gms.  =5.2),  (2  gms.  =1.2). 

Answer  : 

1.  Roast. 

2.  Argol,    1.5  gms. 

3.  Nitre,  11.5    " 

4.  Right  size. 

12.  An  ore  contains  : 


Lead  .......................  15  per  cent. 

Also  sulphur,  antimony  and  iron  in  quantity.     How  should 
it  be  assayed  ? 

13.     One  gramme  of  an  alloy,  cupelled  and  parted,  gave 
silver,  984.2  mgs.  ;  gold,  8.4  mgs.     Wet  assay. 


PEOBLEMS    AND   QUESTIONS.  165 

Added  normal  salt 100  c.c. 

Decime  salt 13    " 

"       silver 3    " 

Strength  of  normal,  101.2  c.c.=l  gramme  pure  silver.    Cal- 
culate the  fineness  of  the  bullion. 

Answer : 

Fineness =983. 28. 

14.  Describe  the  reactions  that  take  place  in  the  nickel 
and  cobalt  assay,  arsenide  method. 

15.  Name  eighteen  principal  reagents  used  in  the  various 
assays,  giving  composition  of  each. 

16.  Describe  the  advantages  and  disadvantages  of  the 
tin  assay,  lead  assay,  iron  assay,  etc. 

17.  Mention    the    ores    of  lead,   tin,   iron,    silver  and 
gold. 

18.  A  sample  presented  for  assay  gave,  on  being  pulver- 
ized and  passed  through  a  sieve  of  80  meshes  to  the  linear 
inch,  the  following  weights  : 

A.  Sifted  ore 1458.32  gins. 

B.  Scales  of  metal 40.75     " 

C.  Total 1499.07  gins. 

It  being  known  from  the  mineralogical  composition  of 
the  sample  that  it  was  a  rich  ore,  J  A.T.  was  taken  for  an 
assay  of  the  sifted  portion  (A).  The  residue  of  metallic 
scales,  etc.  (B),  was  scorified  with  test-lead,  and  yielded  a 
button  weighing  60.35  gms.  This  button  was  rolled  out, 
and  two  average  samples  of  10  gms.  each,  were  cupelled. 

The  following  results  were  obtained  from  the  complete 
assays : 


166  TABLES   AND    REFERENCES. 

A.  SIFTED  ORE. — CRUCIBLE  ASSAY. 
One-third  assay  ton,  9.722  gms.  yielded : 

1.  2.  Average. 

Au  +  Ag 0.19355        0.19275        0.19315 

Au  (by  parting) 0.00025        0.00025        0.00025 


0.19330        0.19250        0.19280 

Agin  litharge 0.00067        0.00067        0.00067 


Ag  in  ore 0.19263        0.19183       0.19213 

The  litharge  yielded  one  milligrm.   silver  per  assay  ton, 
and  two-thirds  assay  ton  were  employed. 

B.  METALLIC  SCALES. 
10  grammes  of  the  scorified  button  yielded. 

1.  2.  Average. 

Au  +  Ag 5.0625  5.0620  5.0622 

Au  (by  parting) 0.0020  0.0020  0.0020 


Ag 5.0605  5.0600  5.0602 

Ag  in  test  lead none  none  none 

A  -i  09-1  q 

A.  Sifted  ore 1458.32x^^0  =28.819  Ag. 

y.  i  &£ 


B.  Metallic  scales..    40.75,    ^^x 60. 35 =30. 538  Ag. 


C.  Total  ore  .......  1499.07  59.357  T'l  Ag. 

29166.66  x  ^'B^I  =1154.71  oz.  per  2000  Ibs. 


A.  Sifted  ore  .....    1458.32  x0'05          =0.0375  Au. 


B.  Metallic  scales..        40.75,  x  60.  35=0.  0121  Au. 


C.  Tofca]  ore 1499.07  0.0496  T'l  Au, 

29166.66  x  ^^=0.9707.  per  2000  Ibs. 


PROBLEMS  AND  QUESTIONS.  167 
EESULT  PEE  2000  LBS.   ORE. 

Silver 1154.71  oz.  at  $1.29 $1489.58 

Gold 0.97  oz.  at  $20.67. . .  20.04 


Total  bullion 1155.97  oz.  $1509.62 

19.  An  ore  of  nickel,  cobalt,  and  copper  gave  the  fol- 
lowing results  from  five  gins,  of  the  original  sample : 

a.  Weight  of  arsenides  from  fusion 2.467  gins. 

b.  "  arsenide  of    cobalt,  nickel, 

and  copper 1.246      " 

c.  "  arsenide  of  nickel  and  cop- 

per      0.542      " 

d.  "       "  button  of  copper  and  gold . .     0. 421      " 

e.  "       "  gold  added 0.150      " 

Calculate  the  per  cent,  of  nickel,  cobalt,  and  copper  in  the 
original  ore. 

Answer:  Cobalt 8.659  per  cent. 

Nickel 1.993       " 

Copper 5.420       " 

20.  Given,  an  ore  of  zinc  : 

10  gms.  of  crude  ore  gave  of  calcined  ore 8.33  gms. 

^  (Kaolin 1.00     " 

Fluxes  added...     Lime>>  0.40     « 


Total 9.73 

Weight  of  iron  buttons  from  fusion 4.53 

"        "  slag  "        "       1.63 


Total 6.16 

Calculate  the  oxygen  for  the  iron,  the  oxide  of  zinc  con- 
tained in  the  ore,  and  the  equivalent  per  cent,  of  zinc. 

Answer  :  Oxygen 1.94  per  cent. 

Oxide  of  zinc...  16.60 
Zinc..  13.32       " 


C?  THE 

UNIVERSITY 


168  TABLES   AND   KEFEREISTCES. 

21.  Given  an  ore  of  iron  which  contains  more  than  is 
required  of  one  of  the  ingredients  of  the  slag,  or  the  silica 
introduced  with  the  kaolin,  when  added  to  that  already 
present,  increases  the  quantity  beyond  the  necessary 
amount.  Required  to  make  up  a  new  slag  with  the  excess  : 

The  ore  10  grammes  ore          T?ormi,wi  Difference  to 

contains  p.  c.  contain  be  added. 

Silica 25.96 2.596 2.50 —0.096 

Alumina 6.92 0.692 1.00 0.308 

Lime,  MgO,    etc.  7.59 0.759 3.00 2.241 

Kaolin  (A1,O,£,  SiO2i)  required  to  furnish  0.308  A12O3  0.616 

Silica  contained  in  0.616  kaolin 0.308 

Silica  in  excess  in  ore . .  . .  0.096 


Total  excess  of  silica 0.404 

Add  fluxes  to  make  up  with  this  excess  more  slag  of  com- 
position as  above : 


-RAmiir^  Difference  to 

Kequned.  be  added 


Silica 0.404 2.50  2. 

Alumina 1.00 1.000 

Lime,  mag.,  etc 3.00 3.000 

Kaolin  required  to  furnish  1.00  A12O3 2.00 

Silica  contained  in  2.00  kaolin 1.00 

Silica  to  be  added,  2.096-1.00 1.096 

Total  material  to  be  added  to  the  charge  : 

Silica 1.096 

Kaolin . . .  .0.616  +  2.00 2.616 

Lime 2.241  +  3.00.. 5.241 

22.  a.  How  much  water  should  be  added  to  6  litres  of  a 
salt  solution  to  make  it  normal,  when  98.6  c.c.  of  the  solu- 
tion precipitates  1  gm.  of  pure  silver  3 

b.  How  much  salt  should  be  added  to  6  litres  of  a  salt 


REFEBENCES    ON   ASSAYING.  169 

solution  to  make  it  normal,  when  100.6  c.c.  precipitates 
1  gin.  of  pure  silver  ? 

Answers  : 

a.  85.09  c.c. 

b.  0.1938  gins. 


REFERENCES  ON  ASSAYING. 

Barstow,  Wm.  :  "Sulphurets;  treatment,  etc.;"  San 
Francisco,  1867. 

Bodemann,  Th.,  n.  Bruno  Kerl  :  "  Anleitung  zur  Berg, 
und  Huttenmannischen  Probirkunst ; "  Clausthal,  1857; 
3d  edition. 

Bodemann,  Th.,  and  Bruno  Kerl :  "  Treatise  on  the  As- 
saying of  Lead,  Copper,  Silver,  Gold,  and  Mercury  ; "  trans- 
lated by  W.  A.  Goodyear ;  New  York,  1865. 

Blossom,  T.  M.:  "On  Gold,  Silver,  and  Iron  ;"  see  Amer- 
ican Chemist  for  1870. 

Budge,  J.  :  "Practical  Miner's  Guide  ;"  London,  1866. 

Byland,  A.  :  "Assay  of  Gold  and  Silver  Wares." 

Kerl,  Win. :  "A  Practical  Treatise  on  Metallurgy  ; "  ed- 
ited by  Wm.  Crooks  and  Ernst  Rohrig. 

Kerl,  Bruno:  "  Metallurgische  Probir-kunst ; "  Leipsic, 
1866. 

Lieber,  O.  M.  :  "The  Assay ers'  Guide." 

Mitchell,  John:  "Manual  of  Practical  Assaying;"  ed- 
ited by  William  Crooks  ;  New  York,  1872. 

Mitchell,  John :  "  Manual  of  Practical  Assaying  ; "  Lon- 
don, 1868. 

North,  Oliver:  "  Practical  Assay  er  ;"  London,  1874. 

Overman,  Frederick:  "Practical  Mineralogy,  Assaying 
and  Mining  ; "  Philadelphia,  1863. 


170  TABLES  AND   REFERENCES. 

Silversmith,  Julius:  " Handbook  for  Miners,  Metallur- 
gists and  Assay  ers." 

Knapp,  F.  :   "  Chemical  Technology." 

Watts,  Henry:  " Dictionary  of  Chemistry;"  London, 
1866-72.  See  under  the  heads  of  the  different  metals. 

See  also  the  annual  reports  of  the  directors  of  the  English 
and  United  States  mints,  which  contain  much  valuable  in- 
formation. 

Besides  the  above,  almost  all  works  on  the  chemistry  of 
the  metals  treat  more  or  less  of  the  assay  of  the  same. 

The  books  mentioned  have  been  given  independent  of 
any  merit ;  there  are  doubtless  many  others  equally  good. 


APPENDIX. 


f  OF  THE 

( "O  l^T  I  V  E  R  S  T  T  ~V  I 

MANIPULATION,  FORMULAE,  >TCU  173 

^^LgAjJFORNJ^^^ 

MANIPULATION,  FORMULA  AND  CALCULATION. 

The  various  operations  of  weighing,  mixing,  charging, 
etc.,  have  already  been  described  under  their  appropriate 
heads  ;  and  it  only  remains  to  give  a  few  hints  on  opera- 
tions peculiar  or  necessary  in  the  performance  of  assays  in 
the  wet  way,  or  analyses. 

PRECIPITATION. — This  operation  is  the  sudden  conversion 
of  a  dissolved  body  into  the  solid  state,  either  by  a  modi- 
fication of  the  solvent,  or  decomposition  with  the  formation 
of  a  new  compound. 

The  separation  of  a  precipitate  is  generally  aided  by  the 
action  of  heat  and  agitation. 

Porcelain  and  glass  vessels  will  be  found  the  best. 

In  adding  the  necessary  reagent  pour  in  carefully  until 
the  precipitate  ceases  to  form  ;  unless  otherwise  directed, 
an  excess  of  the  precipitant  should  generally  be  avoided. 

FILTRATION. — This  operation  has  for  its  object  the  sepa- 
ration of  the  solid  particles  suspended  in  a  fluid,  from  the 
same.  Various  substances  might  be  used  as  a  filter,  but 
the  best  is  unsized  paper,  which  is  prepared  for  the  purpose 
by  cutting  a  circular  form  and  then  folding  it  into  halves 
and  quarters,  so  that  it  will  just  fit  into  a  funnel  and  not 
project  above  the  rim.  For  quantitative  work,  the  prepared 
Swedish  filter  paper  will  be  found  the  best ;  it  should  be 
cut  into  circular  pieces  as  described,  which  should  be  of  a 
constant  size  to  suit  the  funnels  ;  and  the  ash  left  by  burn- 
ing one  of  the  same  carefully  determined.  As  a  rule,  it  will 
be  found  best  to  moisten  the  paper  with  water  before  filter- 
ing, and  to  pour  on  first  the  fluid  portion  of  the  substance 
to  be  filtered. 

DECANTATION. — This  is  simply  a  substitute  for  filtration, 
the  clear  liquor  being  poured  off  from  the  precipitate.  To 
effect  this  the  liquid  is  permitted  to  run  down  a  glass  rod 


174  APPENDIX. 

held  against  the  spout  of  the  vessel,  which  should  be  in- 
clined gently,  so  as  not  to  shake  up  the  precipitate. 

WASHING. — This  is  best  effected  by  using  a  glass  flask, 
fitted  with  a  cork,  in  which  is  inserted  two  glass  tubes,  one 
reaching  to  the  bottom  of  the  flask,  and  bent  to  any  desired 
angle  on  the  outside,  the  end  being  drawn  to  a  point.  The 
second  tube  reaches  to  just  below  the  cork,  and  is  also  bent 
on  the  outside,  but  not  drawn  to  a  point ;  by  blowing  in 
this  tube  the  water  is  expelled  through  the  first.  Warm 
water  will  be  found  the  most  effective.  The  completeness 
of  the  washing  may  be  tested  by  evaporating  a  small  por- 
tion of  the  filtrate  on  platinum  foil,  and  noting  the  residue. 

EVAPORATION. — Porcelain  dishes  are  the  best  for  this 
operation ;  but  if  the  solution  is  to  be  evaporated  to  dry- 
ness  it  should  be  conducted  over  a  water  bath.  A  sand  bath 
may  be  used,  but  care  should  be  taken  to  prevent  loss  by 
spattering. 

IGNITION. — The  washed  precipitate,  after  being  dried,  is 
ignited  to  completely  expel  all  moisture,  or  convert  it  into 
a  constant  or  weighable  substance.  This  is  best  conducted 
by  transferring  to  a  weighed  porcelain  crucible,  and  burning 
the  filter  paper  over  it,  either  on  the  inverted  cover,  or  by 
wrapping  it  in  a  coil  of  platinum  wire  and  holding  it  over  the 
crucible.  The  ash  should  be  heated  until  white,  or  nearly 
so.  The  whole  operation  must  be  conducted  over  a  piece 
of  glazed  paper  until  the  filter  paper  is  burnt,  after  which 
the  crucible  and  contents  should  be  heated  over  a  burner  or 
lamp  ;  gently  at  first.  After  ignition  the  crucible  and  con- 
tents should  be  cooled  in  a  desiccator,  to  avoid  absorption 
of  moisture  from  the  air. 

FORMULAE  AND  CALCULATION. — The  general  methods  of 
calculation  have  been  given  under  the  various  assays,  but 
it  will  be  well  to  bear  in  mind  the  following : 


BLOWPIPE   ANALYSIS,  ETC.  175 

1st.  The  equivalent  of  the  compound  found  is  to  the 
equivalent  of  its  constituent  which  is  sought  as  the  weight 
of  the  compound  is  to  the  weight  of  the  constituent. 

2d.  The  weight  of  the  substance  taken  for  assay  is  to 
the  weight  of  the  constituent  sought  as  one  hundred  is  to 
the  per  cent,  of  thp  same. 

The  equivalents  (atomic  weights)  will  be  found  in  the 
table  on  page  14.  The  equivalent  of  a  compound  being 
equal  to  the  sum  of  the  equivalents  of  the  constituents 
of  the  same.  Thus,  H2SO4  (sulphuric  acid)  is  equal  to 
2  +  32  +  64=98.  The  equivalent  of  hydrogen  (H)  being  1, 
sulphur  (S)= 32,  oxygen  (O)=16.  Two  parts  of  hydrogen 
being  2,  four  parts  of  oxygen =64. 


BLOWPIPE  ANALYSIS,  APPARATUS  AND 
REAGENTS. 

The  assayer  will  find  that  a  knowledge  of  the  proper  use 
of  the  blowpipe  will  prove  a  great  saving  of  time  and 
labor,  by  enabling  him  to  more  fully  understand  the  char- 
acter of  many  substances  presented  for  assay,  which  he 
could  not  otherwise  determine,  save  by  qualitative  analysis. 

The  first  and  most  important  thing  in  blowpipe  analysis 
is  to  learn  to  blow  and  breathe  at  the  same  time,  without 
removing  the  mouth  from  the  instrument  or  interrupting 
the  blast ;  this  can  be  done  by  filling  the  mouth  with  air 
and  breathing  through  tlia  nose,  expelling  some  of  the  air 
into  the  mouth  at  each  breath. 

The  blowpipe  flame  consists  of  two  distinct  portions. 
1st.  The  outside  or  oxidizing  flame.  2d.  The  inner  blue 
cone,  the  point  of  which  is  the  hottest  part  of  the  flame' 
its  action  is  reducing.  This  flame  is  obtained  by  putting 
the  point  of  the  blowpipe  about  one-quarter  of  the  way 
into  the  lamp  flame.  The  true  reducing  flame  is  entirely 
yellow,  the  blowpipe  point  being  held  just  outside  of  the 
lamp  flame. 


176  APPENDIX. 

The  substance  to  be  tested  should  be  finely  powdered 
and  treated : 

1st.  On  charcoal,  in  both  flames. 

This  is  best  done  by  making  a  small  hole  in  the  right- 
hand  corner  of  the  coal,  nearest  the  lamp,  placing  a  little 
of  the  substance  in  the  same,  and  testing  first  with  the  oxi- 
dizing and  then  with  the  reducing  fiame,  noting  the  action 
of  each,  the  formation  of  fumes,  their  odor,  the  fusibil- 
ity of  the  substance,  and  the  color  of  the  coating  formed, 
its  distance  from  the  assay  piece,  etc. 

The  holes  in  the  charcoal  should  be  bored  on  the  edge  of 
the  grain  to  avoid  splintering.  Blow  across  the  coal. 

2d.  If  the  substance  treated  gives  off  fumes  on  charcoal, 
test  a  little  of  it  in  a  closed  and  open  tube  successively, 
first  alone,  and  then  in  the  closed  tube  with  a  little  carbo- 
nate of  soda.  Note  the  coating  or  mirror  formed,  the  color 
and  odor  of  the  fumes  ;  also  decrepitation,  change  of  color, 
etc.  Heat  over  an  alcohol  lamp. 

3d.  Test  the  substance  with  the  borax,  salt  of  phos- 
phorus, and  soda  beads  successively ;  this  may  be  done  on 
platinum  wire  or,  if  the  substance  be  metallic,  on  charcoal. 
To  make  the  proper  sized  bead,  bend  the  end  of  the  wire 
into  a  loop  on  the  point  of  a  sharp  pencil,  dip  it  into  the 
reagent  and  melt  before  the  blowpipe  until  a  clear,  good 
bead  is  formed,  then  add  the  substance  and  heat,  first  in 
the  oxidizing  and  then  in  the  reducing  flame,  observing  the 
color  and  appearance  of  the  bead  in  each  flame. 

4th.  Apply  special  tests,  as  the  color  of  the  flame,  the 
action  of  nitrate  of  cobalt  on  the  coat  formed  on  charcoal ; 
adding  the  cobalt  solution  and  then  heating.  If  the  sub- 
stance is  not  metallic,  its  fusibility  and  the  color  of  the  flame 
can  best  be  noted  by  testing  in  the  platinum-pointed  for- 
ceps. By  moistening  the  material  with  hydrochloric  acid, 
and  bringing  it  into  the  tip  of  the  blue  cone  of  the  blow- 
pipe flame,  the  coloring  power  is  heightened. 

To  get  the  methods  of  performing  the  above  operations 
the  following  substances  will  serve  as  type  examples  : 


BLOWPIPE  ANALYSIS,  ETC.  177 

To  test  blowing  and  flames :  oxide  of  manganese  and 
molybdic  acid,  binoxide  of  tin  on  charcoal. 

To  test  on  charcoal :  lead  and  antimony. 

To  test  in  the  matrass  or  closed  tube  :  cinnabar  and  ar- 
senic. 

To  test  in  the  open  tube  :  stibnite,  sulphur,  and  arsenic. 

To  test  with  the  beads  : 

Borax  bead,  oxide  of  copper. 

Salt  of  phosphorus  bead,  oxide  of  copper  and  sesqui- 
oxide  of  iron. 

Soda  bead,  manganese  and  chromium  compounds. 

CHAEACTERISTIC   TESTS. 

Potassa,  colours  the  flame  violet ;  best  seen  through  a  blue 
glass,  which  shuts  off  the  soda  flame. 

Soda,  reddish-yellow  flame  ;  solution  colors  red  litmus 
paper  blue. 

Lithia,  carmine-red  flame. 

Ammonia,  colors  red  litmus-paper  blue,  pungent  odor. 

Baryta,  burnt  with  alcohol  gives  a  yellowish -green  flame ; 
enamel- white  bead  with  borax. 

Strontia,  crimson  flame  ;  reaction  with  borax  bead,  same 
as  baryta. 

Lime,  colors  the  flame  feebly  red,  becomes  caustic  and 
glows  when  heated. 

Magnesia,  gives  with  nitrate  of  cobalt  a  pale  flesh-color, 
after  long  blowing  ;  best  seen  in  platinum-pointed  forceps. 

Alumina,  gives  a  fine  blue  color  with  nitrate  of  cobalt. 

Silica,  in  S.  Ph.  bead  gives  a  semi-transparent  skeleton 
floating  in  the  glass. 

Oxide  of  antimony,  on  charcoal,  is  reduced  and  gives 
white  fumes  and  coat,  also  greenish-blue  flame.  The  fused 
metal  smokes  after  the  removal  of  the  blowpipe. 

Arsenious  acid,  with  soda  on  charcoal,  gives  white  fumes 
and  garlic  odor.  In  the  closed  tube,  a  metallic  mirror. 

Oxide  of  bismuth,  on  charcoal,  is  reduced  to  metal,  and 


178  APPENDIX. 

gives  an  orange-yellow  color.  A  compound  of  bismuth 
treated  with  a  mixture  of  sulphur  and  iodide  of  potassium, 
on  charcoal,  gives  red  sublimate  of  iodide  of  bismuth. 

Oxide  of  cadmium,  coats  the  coal  with  a  reddish-brown 
powder  and  variegated  tarnish. 

Oxide  of  chromium,  with  soda  in  the  O.  F.  gives  a  yel- 
low glass;  in  R.  F.,  green  on  cooling;  with  S.  Ph.  bead, 
emerald-green. 

Oxide  of  cobalt,  on  charcoal,  becomes  magnetic.  With 
borax  and  S.  Ph.  beads,  smalt-blue  glass. 

Oxide  of  copper,  metallic  button  on  charcoal.  With 
borax  bead,  green  glass,  blue  when  cold ;  red  in  R.  F.  ; 
with  salt,  chloride  of  copper  is  formed,  which  gives  blue 
flame. 

Oxide  of  gold,  with  borax  on  coal,  easily  reducible  to 
metal. 

Protochloride  and  bichloride  of  tin,  when  mixed,  pro- 
duce, even  in  very  dilute  solutions  of  gold,  a  purple  pre- 
cipitate, known  as  purple  of  Cassius,  which  is  insoluble  in 
dilute  acids,  and  may  therefore  be  produced  in  very  acid 
solutions.  The  gold  solution  should  first  be  mixed  with 
bichloride  of  tin,  and  the  pro  to  chloride  then  added  drop 
by  drop. 

"  A  very  delicate  method  of  making  this  reaction  is  as  follows  :  Sesquichlo- 
ride  of  iron  is  added  to  protochloride  of  tin,  until  a  permanent  yellow  color  is 
produced  ;  the  solution  is  then  considerably  diluted.  The  gold  solution  hav- 
ing been  likewise  very  much  diluted,  is  poured  into  a  beaker,  which  is  placed 
on  a  sheet  of  white  paper ;  a  glass  rod  is  dipped  into  the  tin-iron  solution,  and 
afterwards  into  the  gold  solution,  when,  if  even  a  trace  of  the  precious  metal 
is  present,  a  blue  or  purple  streak  will  be  observed."  (Abel  and  Bloxam.) 

Oxide  of  iron,  on  coal, becomes  magnetic.  Borax  bead, 
red  to  yellow  on  cooling  ;  in  R.  F.,  bottle-green ;  with  tin 
on  charcoal,  vitriol-green. 

Oxide  of  lead,  reducible  to  metal  on  charcoal  with  sul- 
phur-yellow coat  and  blue  flame. 

Oxide  of  manganese,  with  soda,  on  cooling,  bluish- 
green.  With  borax,  amethyst  bead,  colorless  in  reducing 
flame. 


BLOWPIPE   ANALYSIS,  ETC.  179 

Oxide  of  mercury,  volatile  on  charcoal,  metallic  mirror 
with  soda  in  closed  tube,  which  unites  with  gold-leaf,  giv- 
ing it  a  white  color. 

Molybdic  acid,  with  S.  Ph.,  yellowish  green,  and  color- 
less when  cold.  The  bead  on  coal  becomes  green  on  cooling. 

Oxide  of  nickel,  on  charcoal,  yields  a  magnetic  powder. 
Borax  bead,  reddish -brown  in  0.  F.  Gray  and  cloudy  in 
R.  F. 

Oxide  of  silver,  on  charcoal,  reducible  to  metal.  With 
borax,  opalescent  or  milk-white  glass.  In  O.  F.  on  char- 
coal, brown  coat. 

Oxide  of  tin,  reducible  on  charcoal  to  metal.  Gives 
yellow  coat,  white  when  cold.  With  cobalt  solution  on 
charcoal  in  0.  F.,  gives  a  bluish-green  color. 

Titanic  acid,  with  salt  of  phosphorus  bead  in  R.  F.,  a 
fine  violet  color. 

Oxide  of  zinc,  yellow  coat  on  coal,  white  when  cold. 
With  cobalt  solution,  green  in  0.  F. 

Chlorine,  with  oxide  of  copper  in  borax  bead,  a  fine 
azure-blue  flame. 

Iodine,  with  soda,  or  better,  bi-sulphate  of  potash  in 
matrass,  violet  fumes,  which  turn  starch  paper  blue.  Green 
flame  with  oxide  of  copper. 

Bromine,  with  bi-sulphate  of  potash  in  matrass,  reddish- 
yellow  vapors  ;  turns  starch  paper  yellow. 

Fluorine  compounds,  etch  glass,  when  mixed  with  a  little 
sulphuric  acid  and  warmed,  the  glass  being  placed  over 
the  mixture. 

Carbonic  acid,  acid  reaction,  turns  lime-water  white. 

Sulphur,  burns  on  charcoal  with  a  blue  flame  with  odor 
of  sulphurous  acid  ;  better  in  open  tube.  A  sulphide, 
when  fused  with  soda,  and  the  mass  moistened  with  water, 
gives  a  black  stain  when  placed  on  clean  silver  foil. 

Boracic  acid,  yellowish-green  flame,  fusible. 

Selenium,  in  O.  F.,  gives  odor  of  decaying  horse-radish. 

Tellurides  and  Tellurium.— The  following  is  a  most 
delicate  and  conclusive  test  for  tellurium :  Treat  a  small 


180 


APPENDIX. 


portion  of  the  mineral  in  0.  F.  on  a  clean  piece  of  porce- 
lain (a  broken  bit  of  an  evaporating  dish  or  other  fragment 
will  answer).  If  tellurium  or  a  telluride  be  present,  a  coat- 
ing will  form,  but  may  not  be  seen  on  the  white  porcelain. 
If,  however,  it  is  moistened  with  a  drop  of  pure  concentrated 
sulphuric  acid,  the  presence  of  tellurium  is  revealed  by  a 
brilliant  carmine  tint  (sulphate  of  tellurium).  The  same 
reaction  may  be  obtained  on  charcoal,  but  when  this  mate- 
rial is  used,  it  becomes  necessary,  after  moistening  the  coat- 
ing with  the  acid,  to  play  upon  it  gently  with  the  flame. 
In  this  case,  the  brilliant  coloring  appears  but  for  an  in- 
stant, whereas,  in  the  first  case,  the  porcelain  has  already 
become  heated,  and  the  carmine  tint  remains  for  some  time, 
and  only  fades  gradually  away. 


SCHEME   FOE   BLOWPIPE   ANALYSIS. 

The  substance  may  contain  As,  Sb,  S,  Se,  Te,  Fe,  Mn, 
Cu,  Co,  M,  Pb,  Bi,  Ag,  Au,  Hg,  Zn,  Cd,  Sn,  Cl,  Br,  I,  CO2, 
SiO2,  HNO,,  H.,O,  &c. 

1.  Treat  on  Ch.  in  the  O.  F.,  to  find  volatile  substances, 
such  as  As,  Sb,  S,  Se,  Te,  Pb,  Bi,  Ag,  Zn,  Cd,  &c. 


a.  If  there  are  volatile  sub- 
stances present,  form  a  coat- 
ing, and  test  it  with  S.Ph. 
and  tin  on  Ch.  for  Sb  ;  or  to 
distinguish  between  Pb  and 
Bi,  using  the  R.  F. 


1).  If  there  are  no  volatile 
substances  present,  divide  a 
part  of  the  substance  into 
three  portions  and  proceed  as 
in  A. 


Sb  gives  gray  bead,  clear  on  long  blowing ;  with  tin  the 
bead  becomes  gray  or  black.  Bi  clear  and  colorless  when 
hot,  blackish-gray  and  opaque  on  cooling  ;  with  tin  the 
glass  becomes  clear ;  Pb  cloudy  and  dark,  but  never  quite 
opaque ;  by  continued  blowing  the  oxide  is  reduced  and 
the  glass  becomes  clear.  In  testing  for  Bi  the  antimony 
must  be  driven  off  first. 


BLOWPIPE   ANALYSIS,  ETC.  181 

If  Sb  is  present  it  is  not  necessary  to  look  for  Bi,  and 
vice  versa.  These  two  substances  are  very  rarely  found 
together.  The  same  is  true  of  Pb  and  Bi. 

2.  If  As,  Sb,  S,  Se5  and  Te  are  present,  roast  a  large 
quantity  thoroughly  on  Ch.  in  the  O.  F.  Divide  the  sub- 
stance into  three  portions,  and  proceed  as  in  A. 

A.  TREATMENT  OF  THE  FIRST  PORTION.  —  Dissolve  a 
very  small  quantity  in  borax,  on  platinum  wire  in  the  O.  F., 
and  observe  the  color  produced.  Various  colors  will  be 
formed  by  the  combination  of  the  oxides.  Saturate  the 
bead  and  shake  it  off  into  a  porcelain  dish. 

a.  Treat  the  bead  on  Ch.  with  a  small  piece  of  silver  or 
gold,  in  a  strong  R.  F.  Lead  can  be  used  instead. 


b.  Fe,  Mn,  Co,  &c.,  re- 
main in  the  bead. 

If  the  bead  spreads  out  on 
the  Ch.,  it  must  be  collected 


c.  M,  Cu,  Ag,  Au,  Sn,  Pb, 
Bi  are  reduced,  and  collect- 
ed by  the  silver  or  gold  but- 
ton. 


to    a  globule  by  continued      Remove  tlie  bntton  from 
blowing.  !tlie   bead  wMle  hot>   or  by 


Make  a  borax  bead  on  pla- 
tinum wire  and  dissolve  in  it 


breaking    the    latter    when 
cold    on  the  anvil  between 


a     ,  -i  a  ,  £    i~l  >   1/V/JLVI.         \JJ-L        UJ-Lyj       c*-iu.  »  -i-i-        KJ^J  u  1 1  \s^s*-m. 

some  of  the  fragments  of  the  |  carefully  preserving 

bead,  reserving  the  rest  f or ,  ^^  fra 

accidents. 


d.     If  Co  is  present,  the 
bead  will  be  blue. 

If  a  large  amount  of  Fe  is 


e.  If  only  Fe  and  Mn  and 
no  Co  be  present,  the  bead 
will  be  almost  colorless. 


present,  add  a  little  borax  to  f^  Look  here  for  Cr,  Ti, 
prove  the  presence  or  absence  Mo,  and  W.  Mo  will  give  a 
of  Co  by  diluting  the  bead,  ]  cloudy-brown  or  black  with 
the  cobalt  color  being  more  the  borax  bead  in  the  R.  F. 


intense. 

If  Mn  is  present,  the  bead 


me  uuictx  ueiiu.  .in  m<^  *•  •  ? 
owing  to  the  molybdic  acid 
being  reduced.  Cr  gives 

when  treated  on  platinum  yellowish-green  with  borax 
wire  in  the  O.  F.  will  become  i  bead ;  yellow  with  soda  bead ; 
dark  violet  or  black.  emerald-green  with  S.  Ph. 


182  APPENDIX. 


Ti  in  S.Ph.  bead,  gives  fine  violet  color ;  best  seen  with 
tin  on  charcoal.  W,  a  fine  bine  color,  under  the  same  con- 
ditions. 

g.  Treat  the  button  on  Ch.  in  O.  F.  with  S.Ph.  bead, 
removing  it  while  the  bead  is  hot. 

n.  If  M  and  Cu  are  present,  the  bead  will  be  green 
when  cold.  If  Ni  only — yellow.  If  Cu  only — blue. 

Prove  Cu  by  treating  the  S.Ph.  bead  with  tin  on  Ch. 
in  the  R.  F.,  the  bead  becomes  red  on  cooling. 

M  and  Cu  may  be  separated  by  fusing  them  with  a  gold 
button  of  equal  weight  and  oxidizing  with  borax  or  S.Ph. 
The  M  is  dissolved  first  in  the  borax  glass. 

i.     For  Ag  and  Au  make  the  special  test  No.  8. 


B.  TREATMENT  OF  THE  SECOND  PORTION. — Drive  off  the 
volatile  substances  in  the  0.  F.  on  Ch.      Treat  with  the  R. 
F.,  or  mix  with  soda,  and  then  treat  with  the  R.  F.,  for 
Zn,  Cd,  Sn.     If  a  white  coating  is  formed,  test  with  cobalt 
solution  and  observe  the  color.      Tin  gives  greenish-blue, 
zinc,  green.     If  Zn  is  found,  it  is  not  necessary  to  look  for 
Sn,  and  vice  versa,  as  they  very  rarely  occur  together.     Cd. 
gives  a  brown  coat  and  variegated  tarnish. 

C.  TREATMENT  OF  THE  THIRD  PORTION. — Dissolve  some 
of  the  substance  in  S.Ph.  on  platinum  wire  in  O.  F.,  observe 
whether  Si02  is  present  or  not,  and  test  for  Mn  with  nitrate 
of  potassa,  and  soda.     If  Mn  be  present  the  bead  will  be 
bluish-green. 

3.  Test  for  As  with  soda  on  Ch.  in  the  R.  F.,  or  with 
dry  soda  in  a  closed  tube.    On  charcoal  it  gives  garlic  odor ; 
in  the  tube,  a  metallic  mirror. 

4.  Dissolve  in  S.Ph.   on  platinum  wire  in  the  O.  F.  (if 
the  substance  is  not  metallic  and  does  not  contain  any  S) 
and  test  for  Sb  on  Ch.  with  tin  in  the  R.  F.     See  1,  a. 


BLOWPIPE  ANALYSIS.  ETC.  183 


5.     Test  for  Se  on  charcoal  in  O.  F.  ;  it  gives  a  horse- 
radish odor. 


6.  In  the  absence  of  Se,  fuse  with  soda  in  the  R.  F.  and 
test  for  S  on  silver  foil.  By  moistening  the  fused  mass 
and  letting  it  stand  on  the  foil  the  latter  turns  black  if  S 
be  present.  In  the  presence  of  Se,  test  in  open  tube,  as  it 
would  interfere  with  the  reaction. 


7.     Test  for  Hg  with  dry  soda  in  a  closed  tube  ;  a  me- 
tallic mirror  is  formed. 


8.  Mix  some  of  the  substance  with  test  lead  and  borax 
glass  and  fuse  on  Ch.  in  the  R.  F.     Cupel  the  lead  button 
for  Ag.    Test  with  nitric  acid  for  Au,  dissolving  the  silver  ; 
cupel  the  residue  with  a  little  pure  lead. 

9.  Test  for  Cl  and  I  with  a  bead  of  S.  Ph.  saturated 
with  oxide  of  copper.     Cl  gives  blue  flame  ;    I,   intense 
green. 

10.  Test  for  Br  with  bi-sulphate  of  potassa  in  a  matrass, 
gives  brownish-yellow  fumes.     Turns  starch  paper  yellow. 

11.  Test  for  H2O  in  a  closed  tube  ;  drops  collect  on  the 
interior.     Test  these  with  blue  and  red  litmus  paper. 

12.  Test  on  platinum  wire,  or  in  platinum -pointed  for- 
ceps, for  coloration  of  the  flame,  moistening  with  hydro- 
chloric acid  first. 

13.  Test  for  C02  with  hydrochloric  acid,  passing  the  gas 
evolved  over  lime-water. 


184  APPENDIX. 


14.  Test  for  HNO3  with  bi-sulphate  of  potassa  in  a  ma- 
trass ;  yellow-colored  fumes,  and  acid  reaction. 

15.  Test  for  Te  in  an  open  tube  ;  forms  a  grayish-white 
sublimate  which  fuses  to  clear,  transparent  drops  when 
strongly  heated.     Te  burns  with  a  bluish-green  flame.    Try 
also  special  test  with  sulphuric  acid. 

The  above  scheme  is  essentially  the  same  as  the  one  used 
by  the  students  of  the  School  of  Mines,  New  York,  pre- 
pared by  Prof.  Thos.  Egleston.  A  few  additions  and 
changes  have  been  made  so  as  to  obviate  reference  to  works 
on  blowpipe  analysis. 

The  abbreviations  0.  F.,  R.  F.,  Ch.,  and  S.  Ph.,  stand 
respectively  for  oxidizing  flame,  reducing  flame,  charcoal? 
and  salt  of  phosphorus. 


BLOWPIPE  APPAEATUS. 

Blowpipe  with  platinum  jet,  in  three  pieces,  with  cylin- 
der to  catch  the  moisture.  Trumpet  mouth-piece. 

Lamp,  for  blowpipe,  with  swivel  and  stand,  four 
pieces. 

Lamp,  alcohol,  with  brass  cover  ground  to  fit ;  for  light- 
ing large  lamp  and  heating  open  tubes,  etc. 

Forceps,  steel,  nickel  plated  (Raynor's),  for  testing  color 
of  flames,  cleaning  platinum  blowpipe  tip,  etc. 

Forceps,  brass,  to  handle  small  buttons,  beads,  etc. 

Forceps,  steel,  for  lamp  to  raise  wick. 

Plyers,  cutting,  for  clipping  minerals,  sampling,  etc. 

Plyers,  flat  nose  (nippers)  for  quantitative  work,  handling 
lead  buttons. 

Holder,  cupel  with  two  cups  and  one  mould,  for  cupel- 
ling lead  buttons. 


BLOWPIPE  ANALYSIS,  ETC.  185 

Holder,  charcoal,  with  platinum  ring  and  shield,  gene- 
rally employed  for  quantitative  work,  but  useful  for  fusing 
samples  of  ore  with  fluxes,  etc. 

Holder  for  evaporating  dish,  with  triangle,  for  parting, 
making  solutions,  etc. 

Holder  for  chimney,  to  concentrate  the  flame  of  alcohol 
lamp,  when  heating  capsules,  etc. 

Holder  for  platinum  wire,  with  six  wires,  for  making 
bead  tests,  or  flame  tests,  if  the  substance  is  very  fusible. 

Holder  for  matrass,  to  hold  tubes,  etc. 

Hammer,  for  breaking  slag,  pounding  buttons,  etc.  ;  for 
chipping  minerals  it  should  have  a  sharp  back. 

Anvil,  for  breaking  slag,  pounding  buttons,  etc. 

Borer,  charcoal,  club  shape,  to  make  holes  in  charcoal  for 
the  assay  piece,  etc. 

Borer,  charcoal,  four-cornered,  to  enlarge  coal  crucibles 
for  quantitative  work  or  fusions. 

Borer,  charcoal,  with  spatula,  for  quantitative  work,  use- 
ful in  boring  out  coals. 

Capsule,  mixing,  brass,  gilded,  to  mix  charges  for  quan- 
titative work. 

Spatula,  mixing,  steel,  for  preparing  charges. 

Spoons,  ivory,  two,  for  measuring  out  reagents,  etc. 

Brush,  assay  button,  for  cleaning  buttons  before  weighs 
ing. 

Charcoal  saw,  to  shape  charcoal. 

Tray,  for  coal,  arranged  to  hold  the  various  sizes  em- 
ployed. 

Tray,  for  dirt,  made  of  japanned  tin. 

Scissors,  for  lamp,  to  trim,  etc. 

Knife,  small,  with  long  thin  blade. 

Magnifier,  with  two  lenses,  to  examine  minerals. 

Magnet,  bar  with  chisel  edge,  to  test  for  iron,  nickel  and 
cobalt. 

Form  for  paper  cylinders,  for  quantitative  work. 

Test  lead  measure, 

Small  camel' s  hair  brushes,  for  cleaning. 


186  APPENDIX. 

Moulds,  for  making  crucibles,  coals,  and  capsules. 

Steel  mortar,  for  crushing  minerals  ;  should  be  well  ten> 
pered. 

Agate  mortar  and  pestle,  for  pulverizing. 

A  small  glass  wash-bottle. 

Small  platinum  spoon  for  fusions. 

Porcelain  streak  plate,  for  testing  minerals. 

Scales  for  quantitative  work,  a  bullion  balance  will  do  as 
well ;  also  a  measuring  scale  for  buttons  (Plattner's).  Glass 
matrasses,  closed  and  open  tubes,  porcelain  dishes  and  cap- 
sules, and  clay  cylinders  to  support  the  coal  crucibles.  Test 
tubes,  one  or  two  funnels,  glass  rods,  and  filter  papers,  will 
also  be  found  serviceable. 

For  quantitative  work  the  assayer  will  also  require : 

Coal  crucibles  and  capsules. 

Clay 

Square  coals  and  covers. 

Total  cost  of  complete  outfit  $75.00. 


BLOWPIPE    KEAGENTS. 

Carbonate  of  soda,  pure,  dry,  and  free  from  sulphur. 

Neutral  oxalate  of  potassa  or  ammonia,  crystals. 

Cyanide  of  potassium,  pulverized.  Not  absolutely  neces- 
sary. 

Iodide  of  potassium,  crystals. 

Borax  and  borax  glass,  pulverized. 

Salt  of  phosphorus  (phosphate  of  soda  and  ammonia). 

Bismuth  flux,  one-half  sulphur  and  one-half  iodide  of 
potassium,  powdered  and  mixed. 

Mtre,  crystals. 

Bisulphate  of  potassa,  pulverized. 

Vitrified  boracic  acid,  in  small  fragments. 

Nitrate  of  cobalt,  in  solution. 

Test  lead,  finely  granulated. 

Tin,  in  foil  best. 


BLOWPIPE   ANALYSIS,  ETC.  187 

Iron.     Wire  in  pieces  of  J"  to  1"  long. 

Gold,  pure,  and  in  foil. 

Arsenic,  metallic,  powdered. 

Test  papers,  blue  and  red  litmus  ;  cut  in  strips. 

Salt,  pulverized  and  dry. 

Sulphur,  flowers  of  sulphur  best. 

Fluorspar,  fine  and  dry. 

Silica,  ground  and  ignited. 

Oxide  of  copper,  pure  and  fine. 

Chloride  of  silver,  in  paste  ;  also  nitrate  of  silver. 

Starch  meal. 

Graphite,  fine  and  pure,  or  powdered  charcoal. 

Concentrated  sulphuric,  nitric,  and  muriatic  acids. 

Acetic  acid  and  ammonia. 

Carbonate  of  ammonia  in  powder. 

Charcoal  cut  in  blocks  3"  x  |"  x  J". 

Sifted  and  washed  bone-ash. 

Starch  paper,  to  test  for  Br,  I,  etc. 

Citric  acid,  tartaiic  acid,  and  iodine,  may  prove  useful  in 
testing  minerals  ;  as  they  can  be  carried  in  the  dry  state, 
and  the  acid  solutions  made  when  required. 


GENEKAL   EEMAEKS. 

To  clean  a  dirty  platinum  point  hold  it  in  the  flame  of 
the  alcohol  lamp  with  the  platinum-pointed  forceps. 

To  clean  platinum  wires,  heat,  and  plunge  into  muriatic 
acid  while  hot. 

To  break  small  pieces  of  mineral,  wrap  in  paper,  tin  foil, 
or  cloth,  before  hammering. 

To  trim  the  wick  of  blowpipe  lamp,  cut  even  with  the 
lamp  and  raise  with  one  point  of  the  steel  forceps  ;  never 
pull  the  wick  up  with  the  forceps, 

To  light  the  usual  blowpipe  lamp,  where  a  heavy  oil  is 
used,  direct  the  flame  of  an  alcohol  lamp  against  the  wick 
until  it  ignites. 


188 


APPENDIX. 


CHEMICAL  APPARATUS  AND  REAGENTS. 


(Qualitative  and  Quantitative.) 


APPARATUS. 


GLASSWARE. 

Lipped  Beakers,  nests  of  six. 
Plain  "          " 

Flasks,  1  oz. 


"      16    "  (pint) 
u       24    " 

3  Litres. 

"      50  c.c.  (measured) 
"     100     "  " 


i  Litre, 

a  -i        u  u 

"        Specific  Gravity. 
Pipettes,  10  c.c. 
100    " 

Gay  Lussac  Burettes. 
Carb.  Acid  Apparatus  (We- 

therelTs). 
Carb.  Acid  Apparatus  (Geis- 

sler'  s). 
Wash  Bottles,  4  oz. 

u  u  g     u 

"          u       16    "  (pint) 

u  u        24    " 

Wash  Bottle  Tubes. 
Funnels,  No.  1  (1^  inch) 

No.  2  (2f     u    ) 
No.  3  (3i     u    ) 
No.  4  (4       "    ) 
No.  5  (5       u    ) 
"         No.  6  (6       u    J 
Watch  Glasses. 
Convex  Covers,  3    inch. 
"  "         3A     u 


Convex  Covers,  4    inch. 


6       ( 

Flat  Covers,        3       < 
u         u  4       ' 

"  5       ' 

"         u(thick)5       ' 

Pieces  Blue  Glass. 

Desiccators  (covered) 

Bottles,  corked,  1  oz. 

u  u  2    " 


3  u 

4  u 

6   u 


u      Glass  stoppered,  -J  oz, 
u     Ito6  " 

Reagent  Bottles  for  desk. 
Glass  Rods  and  Tubes. 
Calcium  Chloride  Tubes. 
Funnel  Tubes. 

"  u     (stop  cocks) 

Ignition  Bulb  Tubes. 
U  Tubes,  set  of  four. 
"       u      No.  1(5^  inch) 
"       "      No.  2  (6       "   ) 
"       u      No.  3  (12     u    ) 
Test  Tubes,  4  inch. 


Specimen  Tubes. 
Retorts,  J  Litre. 


i. 


.REAGENTS. 


PORCELAIN. 
Porcelain  Mortars,  4^  inch. 


"  Ex.  Pestle  for. 
Evap.  Dishes,  nests  of  6. 
12  inch. 


Casseroles, 

a 

a 
a 
n 

Crucibles, 

a 

a 


If 
2 


PAPER. 
Packages  Cut  Filters,  3 


inch. 


Sheets  Swedish  Paper. 

"       Glazed  Paper. 
Note  Books. 
Gum  Tickets. 


METAL. 
Ring  Stands. 
Files,  Triangular. 


Steel  Forceps. 

"      (bent) 
|  Wire  Triangles. 

''  "  (covered)  2  inch, 

u  u  u  o       u 

Scissors. 

Pieces  Wire  Gauze. 

Bunsen  Burners  or  Lamps. 

W^ater  Baths. 

Watch  Glass  Clips. 

Sand  Baths. 

Set  Filter  Patterns. 

Platinum  Foils,  H  inch. 

<  i  ti  O  U 

Wire,  10  feet. 
Crucible,  f  oz. 

Gas  Stoves. 
Blowpipes. 
Clamps. 

SUNDRIES. 

Filter  Stands. 
Test  Tube  Racks. 
Rubber  Tubing,  black,  £  inch. 
u  "        white,i     " 

it  U  U          1         U 

Corks. 

Sponge  Probangs. 
Horn  Spatulas,  4  inch. 


r? 


Towels. 

Test  Tube  Brushes. 
Clay  Chimneys. 
Reagent  Bottles  (extra). 

Total  cost  of  apparatus,  say  $60.00. 


REAGENTS. 


Hydrochloric  Acid  (concent.),  HC1.  Hydrochloric  Acid 
(dilute),  HC1.  Mtric  Acid  (concent.),  HJSTO3.  Mtric  Acid 
(dilute),  HNO3.  Sulphuric  Acid  (concent.),  H2SO4.  Sul- 
phuric Acid  (dilute),  H2S04.  Hydrosulphuric  Acid,  HaS. 


190  APPENDIX. 

Potassic  Hydrate,  KHO.  Sodic  Carbonate,  Na2CO3.  Am- 
monic Hydrate,  (NH4)HO.  Ammonic  Carbonate,  (NH4)2C03. 
Ammonic  Chloride,  (NH4)C1.  Ammonic  Sulphide,  (NH4)2S. 
Ammonic  Oxalate,  (NH4)2C2O4.  Baric  Chloride,  Bad,.  Hy- 
dro-Di-Sodic  Phosphate,  Na2HP04.  Potassic  Ferrocyan- 
ide,  K4Cf  y = 4KCy .  FeCy 2.  Potassic  Ferricyanide,  K6Cf dy = 
6KCy.Fe2Cy6.  Ferric  Chloride,  Fe2Cl6.  Acetic  Acid,  HC2H3O2. 
Calcic  Sulphate,  CaS04.  Mercuric  Chloride,  HgCl2.  Stan- 
nous  Chloride,  SnCl2.  Sodic  Acetate,  NaC2H3O2.  Am- 
monic Sulphate,  (JNH4)2SO4.  Potassic  Bichromate,  K2Cr04. 
Cr03.  Magnesic  Sulphate,  MgSO4.  Lime  Water,  CaH202. 
Calcic  Chloride,  CaCl2.  Plumbic  Acetate,  Pb(C2H3O2)2.  In- 
digo Solution,  C8H5NO.SO3.  Argentic  Nitrate,  AgNO,.  Pla- 
tinic  Chloride,  PtCl4.  Ammonic  Molybdate,  (NH4)2MoO4 
-(-Nitric  Acid.  Ammonic  Sulphocyanide,  (NH4)CNS.  Ba- 
ric Carbonate,  BaCO3.  Sodic  Carbonate  (dry),  Na2C03. 
Borax  (crystallized),  2NaBO2.B203+10H2O.  Phosphorus 
Salt  (crystallized),  Na(NH4)HPO4+4H2O.  Sodic  Nitrate 
(crystals),  NaN03.  Potassic  Cyanide  (powder),  KCy^KCN. 
Cobaltic  Nitrate,  Co(NO3)2.  Ferrous  Sulphate  (crystals), 
FeSO4.  Test  Papers  (blue,  red  and  yellow).  Common  Sul- 
phuric Acid,  H2SO4.  Common  Hydrochloric  Acid,  HC1. 

EXTRA  REAGENTS. — Alphabetical  order: 

Alcohol  (absolute),  C2H5.OH.  Alcohol  (common),  C2HB. 
OH.  Ammonic  Fluoride,  (NH4)F.  Arsenic  (metallic),  As. 
Battery  Acid  (dilute),  H^O^.  Battery  Fluid,  10  parts 
H2O ;  3  parts  H2SO4 ;  1  part  K2Cr2O7.  Benzol  (pure),  C6H6. 
Benzol  (common),  C6H6.  Bromine  Water,  Br+H20.  Chlorine 
Water,  C1  +  H2O.  Chloroform,  CHC13.  Distilled  Water,  H2O. 
Iron  (wire  and  plate),  Fe.  Lead  (bar  and  foil),  Pb.  Mer- 
cury, Hg.  Nitro-Hydrochloric  Acid  (aqua  regia),  HNO3-f- 
3HC1.  Oxalic  Acid  (crystals),  H2C2O4.  Potassic  Iodide 
(crystals),  KI.  Potassic  Carbonate  (dry),  K2CO3.  Potassic 
Nitrate,  KNO3.  Potassic  Nitrite,  KNO2.  Potassic  Chlorate, 
KC1O3.  Potassic  Permanganate  (crystals),  K2Mn2O8,  Silver 
(foil),  Ag.  Sodic  Acetate  (crystals),  NaC2H3O2.  Sulphur 
(roll),  S.  Sulphur  (flowers),  S.  Zinc  (bar  and  sheet),  Zn. 


ASSAYEE'S  OUTFIT.  191 

ASSAYER'S   OUTFIT, 

INCLUDING   THE   MOST   NECESSAEY   AETICLES. 

ARTICLE.  APPROXIMATE  COST 

Ore  Balance $22.00 

Bullion  Balance 65.00 

Weights,  Assay  Ton  and  Gramme 18.00 

Muffles,  J  doz.,  at  75  cents  each 4.50 

Hessian  Crucibles,  50  nests,  small- fives 1.50 

Scorifiers,  500  at  2  cents  each 10.00 

Cupel  Mould 3.50 

Scorification  Mould 1.00 

Crucible,  Scorification,  and  Cupel  Tongs 3.00 

Hammers,  2  at  75  cents 1.50 

Pokers  and  Scrapers 1.50 

Cutting  Shears,  Vise  and  Anvil 5.00 

Files,  Chisels?  Saw,  Hatchet,  etc 2.50 

Iron  Mortars,  large  and  small 3.25 

Plate  and  Rubber 10.00 

Box  Sieve 2.00 

Tin  Sampler 2.00 

Sieves,  wood  frames,  80-mesh 1.50 

Mixing  Scoop 40 

Reagent  Bottles,  glass  stoppered 8.00 

Parting  Bottles 90 

Bottles  for  Samples,  corked 2.00 

Ring  Stands  and  Alcohol  Lamps 1.40 

Wash  Bottles,  two,  one  large,  one  small 90 

Horn  Spatulas,  Spoons,  etc .75 

Parting  Flasks,  Annealing  Cups,  etc 1.50 

Porcelain  Mortar 1.00 

Glass  Rods,  Tubes,  Funnels,   Beakers,  etc 2.00 

Note  Book,  Towels,  Brushes,  etc 1.50 

Extra  Apparatus,  such  as  Iron  Pan  for  mechanical 

assay,  Pipettes,  etc 5.00 

Blowpipe,  Blowpipe-lamp,  etc 6.50 


192  APPENDIX. 

Hammer  and  Anvil,  small $1.65 

Button  Brush 45 

Scissors,  Knife,  Magnifier,  and  Magnet 2.20 

Forceps,  steel  and  platinum 1.75 

Test  Tubes  and  Specimen  Tubes 1.00 

Filter  Papers,  Test  Papers,  etc 1.50 

Platinum  Wire,  Foil,  etc 2.00 

Bone- Ash,  for  making  cupels 5.00 

Litharge 1.80 

Soda,  Borax,  etc. 1. 50 

Test  Lead 6.00 

Nitre,  Argol,  Potassium  Cyanide 4.00 

Nitric,  Muriatic,  and  Sulphuric  Acids 6.00 

Extra  Reagents,  not  mentioned ; .  .  5.00 


Total $219.45 

NOTE. — The  preceding  estimate  is  based  on  the  assump- 
tion that  the  ores  to  be  assayed  will  be  those  of  gold  and 
silver,  and  that  the  method  of  assay  will  be,  as  a  rule,  the 
scorification  process.  No  allowance  has  been  made  for  labo- 
ratory fittings  or  furnaces.  An  ordinary  mason  can  build 
with  brick  and  clay  all  that  is  necessary  at  a  very  small 
cost ;  cupel  furnaces  can,  however,  be  purchased  for  about 
$35,  packed  for  shipment.  The  prices  given  are,  of  course, 
somewhat  approximate,  and  the  list  a  little  full,  but  if  it 
serves  as  a  guide  for  the  beginner  it  will  answer  its  purpose. 


SPECIAL  METHODS  FOR  GOLD  ORES  AND  ALLOYS. 

a.  MECHANICAL  ASSAY. 

Crush  4  to  5  pounds  of  the  sample,  and  pulverize  in  a 
mortar  until  it  will  pass  through  a  40-60-mesh  sieve  ;  then 
wash  in  a  "  Batea,"  which  is  a  conical  pan,  about  20  inches 
in  diameter  and  2^  in  depth  ;  or  in  a  Russia  sheet-iron  pan. 


SPECIAL   METHODS   FOR   GOLD    ORES   AND   ALLOYS.      193 

The  latter  should  be  18-20  inches  at  the  top,  14  inches  at 
the  bottom,  and  sides  5  inches,  sloping  at  an  angle  of  30°-40°. 
The  material  to  be  washed  should  first  be  stirred  up  with 
water  in  the  pan,  and  the  sand  and  dirt  removed  by  a  slight 
circular  jigging  motion,  the  operation  being  conducted 
under  water  ;  to  hold  which  a  small  tub  will  be  found  con- 
venient for  laboratory  purposes.  The  gold  and  heavier 
particles  of  the  ore  will  collect  in  the  bottom  of  the  pan,  and 
can  sometimes  be  separated  by  drying,  and  then  blowing 
off  the  sand,  better  than  by  continued  washing.  A  mag- 
net may  prove  of  service  here.  If  the  ore  is  very  poor,  a 
" color"  of  gold  only  may  be  visible  at  the  end  of  the 
operation. 


b.  AMALGAMATION  ASSAY. 

The  amount  of  free  gold  present  in  an  ore  can  be  deter- 
mined by  grinding  say  18-20  pounds  of  the  finely  pulve- 
rized ore  with  about  2  to  3  oz.  of  mercury  and  a  little  sodium- 
amalgam.  If  mercury  alone  is  employed,  the  addition  of  a 
small  piece  of  cyanide  of  potassium  will  be  found  bene- 
ficial. The  ore  should  be  ground  up  with  water  first,  so  as 
to  form  a  thin  pulp,  and  the  mercury  added  by  squeezing 
it  through  chamois  skin.  This  serves  to  break  the  mercury 
up,  and  facilitates  its  dissemination  through  the  mass  of 
the  ore. 

The  whole  should  then  be  ground  for  2  or  3  hours  ;  this 
can  be  done  on  a  concave  plate,  with  an  iron  rubber,  or  in 
a  hand  "  Arrastre."  To  separate  the  amalgam  formed,  thin 
the  mass  with  water,  and  shake  in  a  pan  or  small  settler  of 
some  kind.  The  lighter  particles  of  dirt  and  ore  float  off, 
and  the  amalgam  finds  its  way  to  the  bottom  of  the  vessel, 
where  it  can  be  collected.  To  separate  the  gold,  etc., 
squeeze  through  chamois  skin  or  fine  leather,  and  heat  the 
residue  in  a  small  iron  retort,  condensing  the  mercury  which 
passes  off.  Scorify  and  cupel  the  gold. 


194  APPENDIX. 

c.  CHLOEINATION  PEOCESS   FOE  THE  ASSAY  or  SULPHU- 

EETS    CAEEYING   GOLD. 

Weigh  out  6  oz.,  and  roast  in  an  iron  pan  coated  with 
chalk  or  clay,  until  no  smell  or  fumes  can  be  perceived  ; 
cool,  grind,  and  roast  again  at  a  strong  red  heat,  then 
moisten  slightly,  and  transfer  into  a  glass  cylinder  8  to  10 
inches  high,  and  2  to  3  inches  in  diameter,  which  is  pro- 
vided with  a  side-opening  near  the  bottom,  through  which 
the  chlorine  gas  can  be  introduced.  The  top  of  the  cylinder 
should  be  fitted  with  a  rubber  cork  and  glass  escape  tube, 
which  passes  into  a  second  cylinder,  containing  blotting 
paper  or  shavings  moistened  with  alcohol.  The  ore  is 
placed  in  the  first  cylinder,  on  a  bed  of  broken  glass  or 
quartz,  which  should  be  deep  enough  to  prevent  the  fine 
ore  from  choking  up  the  opening  through  which  the  gas 
enters.  The  chlorine  is  generated  in  a  Florence  flask,  from 
a  mixture  of  binoxide  of  manganese  (pulverized),  salt,  and 
sulphuric  acid,  then  passed  through  a  wash  bottle,  as  in  the 
case  of  sulphuretted  hydrogen  (see  Fig.  26),  to  wash  it,  and 
into  the  cylinder  containing  the  ore  by  the  lower  side-open- 
ing already  mentioned.  The  flask  containing  the  mixture  for 
the  generation  of  chlorine  should  be  gently  heated,  to  facili- 
tate the  evolution  of  the  gas,  and  the  process  continued 
for  about  two  hours  ;  after  which  the  generating  flask  can 
be  disconnected,  the  rest  of  the  apparatus  being  allowed  to 
stand  for  some  time,  especially  if  the  ore  treated  contain 
galena,  zinc  blende,  etc.  To  extract  the  chloride  of  gold : 
lixiviate  with  warm  water,  acidulate  the  solution  with  a 
little  muriatic  acid,  and  precipitate  with  sulphate  of  iron ; 
warm  and  allow  to  stand  until  clear.  Filter,  wash,  and 
dry  the  gold.  Scorify  filter  and  gold  together,  and  cupel 
button. 

d.  TOUCH-STONE  ASSAY  OF  ALLOYS. 

Alloys  of  gold  can  be  examined  for  their  approximate 
fineness  by  means  of  the  touch-stone  and  nitric  acid.  The 


SPECIAL   METHODS   FOE   GOLD   OEES   AND   ALLOYS.      195 

touch-  stone  is  a  piece  of  black  smooth,  stone  (Basalt  or 
Slate),  on  which  the  alloy  to  be  tested  can  be  rubbed.  The 
streak  left  is  then  tested  with  nitric  acid  in  comparison 
with  the  streak  left  by  an  alloy  of  known  fineness.  Test 
acid  is  sometimes  employed  instead  of  nitric  acid  ;  this  is 
a  mixture  of  nitric  acid  (sp.  gr.  1.34)  98  pts.,  muriatic  acid 
(sp.  gr.  1.17)  2  pts.,  and  distilled  water,  25  pts. 

The  standard  alloys  are  called  touch-needles,  and  consist 
of  pure  gold,  alloyed  in  various  proportions  with  copper, 
silver,  or  both  metals.  They  are  much  employed  by  jewel- 
ers, and  can  be  purchased  ready  for  use. 

Where  the  amount  of  gold  is  small,  the  touch-stone 
method  is  less  accurate  ;  but  for  rich  alloys  and  prelimi- 
nary work,  it  may  prove  useful.  A  sharp  eye  and  practice 
is,  however,  required  to  arrive  at  anything  like  good  re- 
sults. 

e.    SPECIFIC  GEAVITY  METHOD  FOE  THE  DETEEMINATION 
OF  GOLD  IN  AN  ALLOY. 

This  method  is  based  upon  the  principle  that,  in  the 
French  system,  the  volume  of  a  solid  is  equal  to  its  weight 
divided  by  its  specific  gravity,  and  that  since  one  cubic 
centimetre  is  equal  to  one  gramme,  the  volume  of  a  solid 
in  cubic  centimetres  is  equal  to  the  weight  in  grammes  of 
the  water  it  displaces,  when  weighed  in  water.  Weigh  the 
given  alloy  in  air,  and  then  in  water.  (See  method  for 
taking  specific  gravities,  page  151.) 

Let  a  =  Weight  of  alloy  in  air,  in  grammes. 
"   b=         "      "      "      "  water,  in  grammes. 
"    c  =  Specific  gravity  of  gold. 
"    d=        "  "        "  the  other  metal. 

"   x  —  Weight  of  gold  in  the  alloy. 
Then,  a—  x=  the  weight  of  the  other  metal. 

-  =  the  weight  of  water  displaced  by  the  gold  in  the 
c 

alloy,  when  weighed  in  water. 


196  APPENDIX. 

o v 

— g—  =  the  weight  of  water,  displaced  by  the  other  metal 
in  the  alloy,  when  weighed  in  water. 

•jr-  Q  v- 

-  -1-  -—5 —  =  a— b  =  the  total  water  displaced  by  the 
c          ci 

alloy,  or,  to  put  the  equation  in  another  form  : 

-,         -,  ,                        dca— deb— ac 
(d-c)  x  =  dca-dcb— ac,  orx  = ^— —  — . 

.  Knowing  the  numerical  values  of  a,  b,  c,  and  d,  substi- 
tute in  the  equation,  multiply,  subtract,  and  divide  as  indi- 
cated, and  find  the  value  of  x. 

By  applying  this  method  to  a  sample  of  gold  quartz  con- 
taining no  impurities,  such  as  pyrites,  etc.,  the  approxi- 
mate amount  of  gold  in  the  specimen  can  be  determined 
without  crushing  the  same.  The  specific  gravity  of  gold 
can  be  taken  as  19.2,  and  quartz  as  2.6, 


f.    ASSAY  OF  SPECIAL  ALLOYS  OF  GOLD. 

1.  Auriferous   Tin. — Oxidize  in  muffle.      Scorify  with 
Pb,  16  pts.,  Bx.  Glass,  2J  to  3  pts.,  and  cupel  button. 

2.  Auriferous  Mercury. — Distil  if  possible,  and  then  sco- 
rify residue  at  low  heat  with  say  10  pts.  of  pure  lead.    It  is 
best  to  place  the  scorifier  with  charge  in  the  muffle  when 
the  latter  is  cold,  and  let  it  heat  up  with  the  furnace. 

3.  Palladium-gold. — Alloy  with  4  times  its  weight  of 
silver,  and  part  with  nitric  acid.     The  palladium  dissolves 
with  the  silver. 

4.  Rhodium-gold. — Alloy  with  4  parts  of  silver ;  part 
with  nitric  acid,  and  fuse  residue  with  bisulphate  of  potash  ; 
treat  with  distilled  water,  and  dry  and  weigh  the  gold  resi- 
due from  the  fusion.     If  this  is  not  pure,  the  fusion  should 
be  repeated. 

5.  Iridium-gold. — Dissolve  in  nitric  acid  and  hydrochlo- 
ric mixed  (aqua  regia) ;  wash  and  weigh  the  iridium,  which 
remains  as  a  black  powder. 


OUTLINE  EXAMINATION   SCHEME   FOR  ASSAY.  197 

6.  Gold  containing  platinum. — Alloy   with  excess  of 
silver,  and  part.     See  Platinum  Scheme,  page  121. 

7.  Gold   Sweeps,   etc. — Burn,   and  if  any  particles  of 
metal  are  apparent,    sift,  and  assay  scales  and   siftings 
separately.     See  Assay  of  Gold  and  Silver  Ores.     The  pre- 
cious metals  can  also  be  separated  by  amalgamation,  the 
tailings  from  amalgamation  being  assayed  by  the  crucible 
method  for  gold  and  silver.     The  buttons  from  cupellation 
may  contain  platinum. 


OUTLINE  EXAMINATION  SCHEME  FOR  THE 
ASSAY  OF  ORES. 

The  ore  may  contain :  gold,  silver,  lead,  antimony,  bis- 
muth, tin,  mercury,  zinc,  platinum,  copper,  iron,  nickel, 
cobalt,  sulphur,  arsenic,  tellurium,  selenium,  etc.  Required 
to  determine  gold,  silver,  and  useful  metals. 

a.  Inspect  with  magnifying  glass.  Test  with  blowpipe. 
Sample,  pulverize  and  sift.  If  scales  remain  on  sieve,  test 
with  magnet,  as  they  may  come  from  mortar ;  if  not  mag- 
netic, weigh  residue  and  siftings,  and  assay  separately. 
Calculate  value  as  directed,  page  75. 

5.  Treat  scales  by  scorification  for  gold  and  silver.  For 
other  metals,  treat  as  an  alloy,  by  wet  methods. 

c.  Charge:  ore  10  gms.,  cyanide  of  potassium  30  gins., 
in  No.  5  crucible,  and  fuse  in  a  quick  fire  ;  cool,  break,  and 
weigh.  The  button  may  contain  lead,  antimony,  bismuth, 
tin,  iron,  etc.  Test  by  blowpipe.  If  lead,  determine  by 
muffle  method,  page  58.  If  tin,  antimony,  or  bismuth, 
duplicate  by  cyanide  fusion.  If  iron,  run  charges  for  un- 
known ores,  page  95.  If  tin  is  present,  it  will  not  be  neces- 
sary, as  a  rule,  to  look  for  other  metals.  The  button  from 
the  cyanide  fusion  should,  however,  be  treated  as  an  alloy. 


198 


APPENDIX. 


d.  Run  preliminary  assay  (see  page  66)  ;  weigh  lead 
button  to  determine  reducing  power  (R.  P.)  ;  cupel  the  lead 
button  to  determine  approximate  richness  of  ore.  Notice 
the  color  of  cupel,  to  decide  as  to  presence  of  copper.  The 
reducing  power  may  be  : 


No.  1.  None. 
Ore    probably 
poor,  no  S,  As,  Sb, 
etc. 

Charge  : 
Ore             1  A  T 

No.  2.  Low. 
Ore  rich  or  poor, 
little  S,  As,  Sb,  etc. 

x.  Bead  from  pre- 
liminary    cupella- 
tion  large. 

No.  3.  High. 
Ore  rich  or  poor, 
much    S,   As,    Sb, 
etc. 

x.  Bead  from  pre- 
liminary    cupella- 

Litharge.  50  gms. 
Soda....   2  A.T. 

Run  scor.  assay  : 
Ore  i  A.T. 

tion  large. 

"Rl1H   SsPAVlfi  Pfl  "I"!  ATI 

Argol  ...  2  gms. 
Bx.  Gls..lO     " 
Silica...!  15     " 
Salt  .  .    .  .  cover. 
Use  Hessian  cruci- 
ble.    Cupel  button 
from  fusion,  or  else 
run  scorification  as- 

Lead  40  gms. 
Borax   Glass    as 
required. 

y.  Bead  from  pre- 
liminary    cupella- 
tion  small. 

Charge  : 
Ore             1A.T. 

assay  : 
Ore.  4  to  ^  A.  T. 

Lead  ...  40  gms. 
Borax   Glass    as 
required. 

y.  Bead  from  pre- 
liminary    cupella- 
tion  small. 

Qttj)   Lcilvlll^Jj  O  feOUll- 

fiers,  £  A.T.  of  ore 
in  each.     Combine 
and  cupel  buttons. 
Observe    color    of 
cupel  after  cupella- 
tion  to  detect  pres- 
ence of  copper,  also 

JlTl'nPflT'ilTIPP       O"f 

Litharge.  50  gms. 
Soda  ....   1A.T. 
Silica  ....  15  gms. 
Bx.Gl.  5-10     " 
Argol  or  nitre  ac- 
cording to  calcula- 
tion from  reducing 
power.      See   page 

Roast  2  A.T.  of 
ore,   and   charge 
with 
Litharge.  50  gms. 
Soda  ....   1  A.T. 
Silica....  1     " 
Charcoal.  J-l  gm. 
Salt          cover 

bead,    which    may 
contain    platinum, 
or  non  -  oxidizable 
metals,  if  any  were 
present  in  the  ore. 

67.     Can  run  num- 
ber of  scoriliers,  % 
A.  T.  of  ore  each, 
and    cupel    united 
buttons,  as  in  the 
case  of  No.  1. 

In   Hessian    cruci- 
ble, or  use  special 
methods,     accord- 
ing to  character  of 
the  ore.     See  pages 
77-79. 
Can  run  number 
of  scoriliers,  as  in 
No.  2. 

EULES   FOR  THE   EXAMINATION   OF  A   MINE.  199 


e.  If  button  freezes  in  process  of  cupellation,  the  furnace 
being  hot,  and  the  cupel  unsaturated,  copper,  cobalt,  nickel, 
tin,  or  platinum  may  be  present ;  cupel  dark  brown  or  red 
after  cupellation,  probably  copper. 

1.  Determine   cobalt,    nickel  and   copper  by  arsenide 
method,  pages  91,  99-102. 

2.  For  platinum,  treat  button  as  an  alloy,  page  121. 

3.  Tin  :  run  special  assay,  section  c. 

f.  If  the  preliminary  blowpipe  test  indicates  the  pres- 
ence of  mercury,  zinc,  or  tellurium,  etc.,  the  ore  should  be 
run  by  scorification  method  for  gold  and  silver.  For  ores 
containing  mercury  the  heat  should  be  very  low,  at  first, 
and  increased  gradually.  For  tellurides,  see  page  79. 

The  zinc  and  mercury  may  be  determined  by  the  meth- 
ods given  on  pages  82  and  84  ;  or,  if  the  ores  are  impure, 
by  the  wet  way. 

NOTE. — The  above  scheme  is  designed  as  a  guide  for  be- 
ginners. The  experienced  mineralogist  and  assayer  will 
generally  be  able  to  foretell  the  character  of  the  ore,  and 
select  his  method. 


RULES  FOR  THE  EXAMINATION"  OF  A  MINE. 

The  following  suggestions  are  taken  from  an  article  pre- 
pared by  Mr.  C.  B.  Dahlgren,  and  as  an  outline  guide  may 
prove  useful. 

1.   THE  HISTORY  OF  THE  MINE  (TRADITIONS)  AND  PERFECT 

TITLES. 

All  existing  data  of  the  mine,  as  pamphlets,  maps,  ores, 
assays,  records  of  work  done,  traditions,  etc.,  should  be 
collected  and  carefully  studied. 

The  mining  laws  of  the  district  should  be  fully  under- 


200  APPENDIX. 

stood,  so  that  a  perfect  title  may  be  given  to  the  pur- 
chaser. Usually  this  branch  of  the  business  goes  through 
a  lawyer's  hands.  In  the  United  States,  the  usual  transfer 
of  a  U.  S.  Patent  or  Recorder's  Titles  are  sufficient.  But, 
in  Mexico  (while  well  enough  to  have  the  former  owner  or 
worker's  transfer),  as  no  "fee  simple"  to  mines  exists,  a 
mine  must  be  worked  and  transferred  in  accordance  with 
the  " Mining  Ordinances." 

2.  GEOGRAPHICAL    POSITION  —  MAP  OF    ROADS   TO   AND 

DISTANCES    FROM    RAILWAYS,    STEAMERS,    FREIGHT, 
ETC. 

Accurate  maps  should  be  prepared  of  the  county,  and 
mining  district,  giving  the  roads  and  distances  to  the  near- 
est railway,  steamers,  or  stages,  or  other  lines  of  communi- 
cation or  transportation.  Statistics  may  be  made  out  of 
freights,  fares,  time-tables,  etc.,  from  the  proper  relia- 
ble sources. 

3.  CLIMATE,    WATER,    FUEL,    TIMBER,  CHARCOAL,  SALT, 

BUILDING  MATERIALS  (LIME,  CLAY,  STONE),  SULPHUR, 
AGRICULTURAL  RESOURCES,  ETC. 

Careful  observations  should  be  made  as  to  the  climate, 
acres  of  fuel  or  timber,  number  of  inches  of  water  for  mill- 
ing purposes,  salt,  sulphur,  lime,  building  materials,  agri- 
cultural resources,  and  supplies. 

Extravagant  terms  should  be  avoided,  and  precise  and 
concise  statistics  alone  taken  and  offered  to  the  interested 
parties. 

4.  GEOLOGICAL  STRUCTURE  OF  COUNTRY  ROCK. 

The  capitalist  usually  cares  very  little  whether  the  mine 
is  in  diorite,  quartzite,  Silurian  limestone,  or  is  a  contact 
vein,  as  long  as  pay  ore  is  found  in  sufficient  quantities  to 
declare  dividends.  Do  not,  therefore,  indulge  in  theories 
as  to  the  formation  of  lodes,  etc.,  but  allude  only  to  plain 
practical  "facts"  in  a  clear,  concise  manner.  Sketches 


EULES   FOR  THE   EXAMINATION   OF   A   MINE.  201 

and  photographs  will  be  very  appropriate,  usually  convey- 
ing quicker  and  clearer  impressions  of  the  subject  under 
examination  than  any  amount  of  words. 

5.  SIZE  AND  STRUCTURE  OF  YEIN,  WITH  MAP  OF  ALL  WORK 

DONE,  IN  PLAN,  ELEVATION,  AND  SECTION,  GIVING 
COURSE,  DIP,  WIDTH  OF,  AND  CHARACTER  OF  WALLS, 
FAULTS,  BREAKS,  HORSES,  SLIDES,  CROSS  COURSES, 
ETC. 

Correct  and  complete  maps  (in  plan,  section,  and  eleva- 
tion) should  be  made,  giving  the  "  course,  dip,  width  of, 
and  character  of  walls,"  faults,  horses,  slides,  breaks, 
cross  courses,  ore  seams,  etc.,  and  barren  rock,  water,  all 
work  done,  etc.  These  will  constitute  a  principal  part  of 
the  examination  ;  they  should  be  accompanied  by  sketches 
or  photographs,  and  will  show  the  "  probabilities,"  as  to 
the  direction  and  force  of  the  vein,  which  may  rationally 
be  indulged  in. 

A  plan  for  working  the  mine  to  best  advantage  (both 
immediate  and  future),  may  close  this  section. 

6.  CHARACTER  AND  QUALITY  OF  THE  ORES  (ASSAYS  AND 

ANALYSES)  AND  GANGUE. 

A  knowledge  of  the  blowpipe  will  be  of  great  use  here 
for  preliminary  determinations  (qualitative);  while  the  assay 
furnace  will  be  needed  to  settle  the  practical  values  of  the 
ores  in  question.  If  possible  (i.e.,  if  facilities  exist)  an 
analysis  will  not  be  out  of  the  way.  We  now  come  to  the 
sampling.  Careful  samples  of  ores  at  any  mill  or  reduc- 
tion works,  and  of  tailings,  or  slags,  should  be  made.  They 
should  be  average  samples.  These  should  be  assayed,  and 
values  per  ton  estimated  as  well  as  the  per  cent,  reached 
in  the  working.  Extreme  caution  should  be  exercised  in 
order  that  no  "salting"  can  be  perpetrated.  A  careful 
record  should  be  kept  of  these  results.  Having  determined 
the  ores,  extracted,  the  mine  should  be  visited  and  sampled 
in  all  its  workings  and  croppings.  A  map  should  be  taken 


202  APPENDIX. 

along  to  mark  the  localities  of  the  samples,  and  they  should 
be  carefully  numbered  and  recorded,  as  well  as  the  results, 
which  should  not  be  known  to  outsiders.  Each  sample 
should  be  sacked  and  sealed  under  the  eye  of  the  expert. 
Samples  should  be  selected  at  random,  to  avoid  the  least 
possibility  of  collusion. 

7    QUANTITY  OF  (PEOBABLE  SUPPLY   OF)  PAY  OEE  (DE- 
DUCED FROM  WORK  DONE  AND  PROBABILITIES). 

This  is  the  important  part  of  the  report,  and  for  which  it 
is  made.  The  ore  in  sight  will  serve  as  one  of  the  most 
important  guides  towards  determining  this  fact.  The  other 
is  the  "probability"  of  a  continuance  of  the  ore,  which 
experience  and  the  result  of  observations  made  (see  Section 
5)  will  aid  in  determining. 

8.  COST  OF  MINING,   HAULING,  AND   MILLING  (WAGES, 

MATERIALS,  FREIGHTS,  ETC.) 

This  depends  on  the  price  of  labor,  supplies,  fuel  and 
timber,  freights  on  machinery  and  supplies,  taxes,  etc. 

This  part  of  the  examination  is  not  a  difficult  one.  In 
California,  the  cost  of  milling  is  from  $2  to  $4  per  ton 
(whether  by  steam  or  water  power),  as  also  in  the  Black 
Hills.  In  Nevada  (on  silver  ores),  it  runs  from  $9  to  $20 
per  ton.  Comstock,  $11.00.  Formerly  the  cost  of  quick- 
silver was  a  very  heavy  item,  but  at  date  it  is  very  mode- 
rate. 

9.  METHOD  OF  REDUCTION  (WHETHER  BY  AMALGAMATION, 

LIXIVIATION,  OR  SMELTING). 

The  report  should  embody,  at  this  point,  a  clear  state- 
ment of  the  most  efficient  method  of  working  the  mine,  and 
of  reducing  the  ores.  An  analysis  will  determine  whether 
by  smelting,  amalgamation  (raw,  or  roasting),  or  by  leaching. 
It  may  in  some  instances  be  found  to  be  more  profitable  to 
concentrate,  and  ship  the  product. 


RULES  FOE  THE  EXAMINATION  OF  A  MINE.         203 

10.  AVOID  BEING  SALTED. 

Never  lose  sight  of  this  injunction  from  first  to  last,  but 
see  to  all  the  important  points  personally. 

11.  REQUISITES  FOE  A  SUPEEINTENDENT. 

A  superintendent  should  understand  assaying,  survey- 
ing, chemistry,  machinery,  and  book-keeping,  so  that  in 
no  branch  of  the  business  can  he  be  deceived.  It  is  not 
possible  for  one  man  to  do  all  of  these  things  at  once,  but 
he  should  be  able  to  inspect  every  department  understand- 
ingly.  A  knowledge  of  law  is  sometimes  very  essential. 


ZETTNOWS   SCHEME   FOR   QUALITATIVE   AN 

ARRANGED    BY    H.     CJ 

For  the  Students  of  the  Sc 
Add  hydrochloric  acid  to  the  solution,  wash,  and  filter. 


Precipitate. 
Boil  with  water  and  filter. 


Filtrate. 
Add  excess  of  dilute  H2SO4  and  wash  on  filter. 


Solu- 
tion. 
Add 
H2S04 


Preci- 
pitate 
Pb 


Residue. 

Treat  with 

(NH4)HO 


Precipitate. 

Agitate  with  considerable  cold 
water  and  filter. 


Solu- 
tion 
Add 
HN03 


Preci- 
pitate 


Residue 

turns 

gray  or 

black 

Hg 


Filtrate. 
Add  excess 

of 
(NH4)2C204 


Precipitate 
Ca 


Residue. 
Add  (NH4)  HO  and 

(NH4)2C4H408 
digest  and  filter. 


Residue. 

Boil  with  Na2CO3, 

liter,  wash,  dissolve 

on  filter  with  HC1, 

neutralize  filtrate 

with  (NH4)HO,  and 

divide  into  two 

parts. 


Filtrate. 
Add 

HCC.HgO,) 

and  K2CrO4 


Precipitate 
Pb 


1st  Half. 
Add  excess 
of  solution 

of  SrS04 


Predpitat 
Ba 


Second  Half. 
Add  excess  of 
HoSi3Fl6  and  alcohol. 
Shake,  filter,  dilute 
with  water,  expel 
alcohol  by  evapora- 
tion, add  solution  of 
CaSO4,  and  after  one 
or  two  minutes  a 
precipitate 
Sr 


In  this  scheme  regard  is  had  to  the  following  substances 
in  aqueous  solution  : 

I.  PbO,  Ag2O,  HgO 

H.  CaO,BaO,SrO 

III.  (NH4^20,Na20,K2O 

IV.  Ap2O3;As2O5,Sb2O3,Sb2O5,SnO,SnO2,Hg2O,CuO, 

V.    FeO,Fe2O3,Cr2O3,Al2O3 
VI.    MnO,MgO,CoO,NiO 
VII.    ZnO 


Filtrate. 
Divide  the  solution  into  tw 


To  i  add  BaH2O2  and 
boil. 


Volatilized 
(NH4)2O 
Test  gas 
with  HC1 
and  litmus. 


Solution 

Add 
excess 

(NH4)2C03 

and 

(NH4)aC204 
warm,  filter, 
evaporate  to  dryness, 

and  ignite  residue. 
Test  on  platinum  wire 
in  colorless  flame  ;  in- 
tense yellow  color  in- 
dicates 

Na. 

Violet  color  seen 

through  blue  glass 

indicates 

K 


Place 
li 


Vola 
tilizec 
Collec 
spots 
cold 
porce 
lain 
and 
treal 
with 
NaCl 
Spot 
dis- 
solve 
As 
Spot 
do  no 
dis- 
solve 
Sb 
Test 
also 
with 
AgNC 


N.  B.  To  test  for  zinc  mix 
filter,  add  NaHO  in  excess,  a 
trate^  boil  until  all  odor  of  (N 
solution,  a  cloud  or  precipitate 


YSIS   WITHOUT   THE   USE   OF  H,S   OR   (NH^HS. 

[NGTON    BOLTON,    PH.D., 

1  of  Mines,  Columbia  College. 


equal  parts,  J  and  J. 


the  solution  in  a  Marsh's  apparatus,  add  pieces  of  zinc  and  a  strip  of  platinum  foil,  when  but 
dnc  remains  heat  15  or  20  minutes,  and  throw  contents  of  flask  on  a  filter  ;  wash  thoroughly. 


Residue. 
Treat  with  strong  HNO3,  and  filter. 


Filtrate 

)il  with  a  little  HNO3  and  divide  into  two  un- 
equal parts. 


Residue. 
i'ash,  boil  with 
(ICl  and  filter. 

Filtrate. 
Divide  into  two  parts. 

Solu- 

Resi- 

1st Half. 

Second  Half. 

tion. 

due. 

Add  HC1,  boil,  then 

it  in  a 

Add  to 

SnCl2 

add  excess  of  NaHo,  1 

>lati- 

solution 

wash  the  precipitate,! 

num 
dish 
>itha 
•>ce  of 

num 
dish, 
boil 

Precipi- 
tate. 

on  uicer  witn  water,  i 
then  with  (NH4)HO 
containing  NH4C1. 

zinc. 

with 

Hg1 

dark 

HC1, 

iot  on 
e  pla- 
inum 
indi- 
cates 
Sb 

filter 
and  add 
HgCl2 
Preci- 
pitate. 
Sn 

Residue. 
Dissolve  on 
filter  in  very 
little  HC1 
and  add 

Filtrate. 
Divide  into  two 
parts. 

large  quan- 
tity of  H2O 
to  the  fil- 

1st Half. 
Acidify 
with  HC1 

2d  Half] 
Add 
excess  of 

trate.    A 
cloudy  pre- 
cipitate in- 
dicates 

and 
add 
K4Fe2Cy8 

NaHO, 
a  white 
gelatin- 
ous 

Bi 

Precipi- 

Precipi- 

tate. 

tate 

Cu 

Cd 

1st  Portion. 

Add  KCyS 

Red  Color 

Fe* 


Second  Portion. 
Neutralize  with  (NH4)HO,  add  ex- 
cess of  Ba  CO3,  agitate  ten  min- 
utes, filter  and  wash  thoroughly. 


Precipitate. 

Boil  in  a  porcelain 
dish  with  dilute 
H,S04  and  filter. 

A.dd  excess  of  NaHO 
to  filtrate,  a  few 
drops  of  KMnO4 

and  a  little  NH4C1, 
boil,  filter,  and 

divide  the  solution. 


1st  Half. 

Add  some 

H(C2H,02) 

and 


Cr 


Half. 

Add 
excess 

of 
NH4C1 


Filtrate. 
Add  excess  of  dilute  H2SO4, 
filter  and  saturate  filtrate 
with  (NH4)2CO3>  warm,  fil- 
ter, and  wash. 


pitate 


*  To  determine  de- 
of  oxidation  of 
,  examine  the  ori- 
inal  solution  with 
:4FeaCy6  and  KCyS 


)rtion  of  the  original  solution  with  HC1,H2SO,, 
.oil.  Add  a  little  (NH4)2CO3  and  NH4C1  to  fil- 
10  is  expelled,  and  filter.  Add  K4Fe2Cy,  to 
nates  Zn. 


fate. 
Mix  a  por- 
tion with 
Na2C03 

and 

NaNO3, 
fuse  on 
platinum 

foil. 

Green 

color. 

Mn 


Dissolve 

another 

portion  in 

HC1,  neu- 

tralize 

with 

(NH4)HO 

add  con- 

siderable 

NH4C1  and 


Precipi 
fate 
Ca 


Solution. 
Add  Na2HPO4 


Preci- 
pitate 
Mg 


Solu- 
tion. 
Evapo- 
rate to 
dryness, 
dissolve  in  HC1, 
add  KN02  and 
H(C?H302), 
filter. 


Preci- 
pitate 
Co 


Solu- 
tion. 
Add 
NaHo 


Preci- 
pitate 
Ni 


=    LIBRXSy 

'UNI 

OF 


INDEX. 


A. 

PAGE 

ADJUSTING  BALANCES 19 

Agents,  Sulphurizing 44 

Alloys  and  Gold  Ores,  Special  Me- 
thods   192 

Gold 147 

Gold,  Lead  for  Cupel  lation. .  .  155 

Gold,  Special  Assay  of 196 

Silver 146 

Touch-stone  Assay  of 194 

Amalgamation  Assay  of  Gold  Ores.  193 

Ammonia,  Carbonate  of 44 

Annealing  Cup 38 

Antimony,  Assay  for 61 

Ores 61,  142 

Remarks  on 63 

Sources  of 61,  142 

Apparatus,  Assay 37 

Blowpipe 184 

Chemical 188 

Gold  Bullion 118 

Silver  Bullion 112 

Appendix 172 

Argol 42 

Assay,  Chlorination 119 

Chlorination,  Remarks  on.  ...  119 

Crucible  for  Gold  and  Silver .  65 

for  Bismuth 85 

for  Carbon 102 

for  Cobalt 99 

for  Copper.  .    91 

for  Iron 94 

for  Mercury 83 

for  Nickel 99 

for  Platinum 80 

for  Tin 87 

for  Zinc 82 

of  Alloys,  Touch-stone 194 

of  Gold  and  Silver  Ores 64 

of  Gold  Ores,  Amalgamation .  .  193 

of  Gold  Ores,  Mechanical 192 


Assay  of  Gold  Sweeps 197 

of  Ores,  Examination  Scheme 

for 197 

of  Ores,  Preliminary 66 

of  Silver  Bullion 109,  111 

of  Silver  Bullion,  Preliminary.  110 

of  Special  Alloys  of  Gold 196 

of  Tellurides 78 

Volumetric  for  Iron 131 

Weights 20,  149 

Assays,  Fire 55 

Wet 106 

Assayer's  Outfit 191 

Assaying,  References  on 169 

Atomic  Weights 14 

Avoirdupois  Weights 148 

B. 

Balances  and  Weights 18 

to  Adjust 19 

Base  Metals,  Assay  Report 157 

Beads,  Weighing  of 52,  74 

Bi-Carbonate  of  Soda 40 

Bismuth,  Assay  for.  ...    85 

Determination  of  in  Alloy. .  .  .  124 

Ores 85,  143 

Remarks  on 86,  125 

Sources  of 85,  143 

Black  Flux  Substitute 41 

Blowpipe  Analysis,  etc 175 

Analysis,  Characteristic  Tests  177 
Analysis,  General  Remarks  on  187 

Analysis,  Reagents 186 

Analysis,  Scheme  for 180 

Apparatus - .  184 

Test  for  Tellurides 179 

Borax 40 

Box  Sieve 35 

Bullion,  Apparatus  for  Silver 112 

Assay  of  Silver 109 

205 


206 


INDEX. 


Bullion,  Cupellation Ill 

Gold 115 

Gold,  Assay  Report 161 

Gold,    Cupellation    for    Base 

Metal 115 

Gold,  Parting 116 

Gold,      Platinum      Apparatus 

for 118 

Gold,  Remarks  on 117 

Preliminary  Assay  of 110 

Remarks  on  Silver 113 

Silver 109 

Silver,  Assay  Proper Ill 

Silver,  Assay  Report 162 

Weighing 52 

Button,  Lead 71 

C. 

Calcination  and  Roasting 50 

Calculation  and  Formula? 174 

of  Results 75 

Calorific  Value  of  Fuel 103 

Capsule,  Porcelain 75 

Carbon,  Assay  for 102 

Remarks  on 104 

Sources  of 102,  145 

Carbonate  of  Ammonia 44 

Cements,  Lutes,  and  Washes 31 

Characteristic  Tests,  Blowpipe  An- 
alysis   177 

Characteristics  of  Metals 140 

of  Ores 142,  147 

Charcoal 42 

Lined  Crucibles 28 

Chemical  Apparatus  and  Reagents  188 

Chemicals  and  Reagents 39,  189 

Sundry 45 

Chlorination  Assay 119 

Process  for  Gold  Sulphurets . .  194 

Cobalt,  Assay  for 99 

Nickel  and  Copper,  Composi- 
tion of  Arsenides 101 

Ores 99,  144 

Remarks  on 101 

Sources  of 99,  144 

Coins,  United  States 148 

Comparison  of  Units 150 

Composition  of  Arsenides  of  Nickel, 

Cobalt  and  Copper 101 

Copper,  Assay  for 91 

Nickel  and   Cobalt,   Composi- 
tion of  Arsenides 101 

Ores  90,  143 

Remarks  on 93,  130 

Scheme  for 128 

Sources  of 90,  143 


PAQB 

Corrections   for  Loss   of  Silver  in 

Cupellation Ill 

Crucible  Assay   for  Gold   and  Sil- 
ver      65 

Assay  Report  for  Base  Metals,  157 

Assay  Report  for  Iron 158 

Assay,    Silver    and    Gold   Re- 
port     159 

Tongs 32 

Crucibles 26 

Charcoal  lined 28 

to  Line 32 

Wash  for 32 

Cubic  Measure,  English 150 

Measure,  French 150 

Cup,  Annealing 38 

Cupel  Moulds 35 

Tongs 33 

Cupels 29,  30 

Cupellation 52,  71 

for  Base  Metal,  Gold  Bullion. .   115 
Silver  Bullion Ill 

Cyanide  of  Potassium 41 


I). 


Decantation 173 

Desk,  Laboratory 36 

Distillation  and  Sublimation .  .  51 


E. 

Elements,  Table  of 14 

English  Cubic  Measure 150 

Evaporation 174 

Examination    of    a    Mine,    Rules 

for 199 

Scheme  for  the  Assay  of  Ores.  197 

Extra  Reagents 190 


Ferro-Cyanide  of  Potassium 41 

Filtration 173 

Fire  Assays 55 

Flask,  Parting 38 

Fluxes  for  Scorification  Assay 69 

Formula  and  Calculation 174 

French  Cubic  Measure 150 

Liquid  Measure 149 

Weights 149 

Fuel,  Calorific  Value  of 103 

Fuels  and  Furnaces 21 

Furnaces  and  Fuels 21 

Calcining 21 

Fusion,  etc 21 


INDEX. 


207 


PAGE 

Furnaces,  Muffle 22 

Scorification 23,  25 

Fusion  and  Reduction 51 

Gold  and  Silver  Ores. .  .  68 


G. 

Galena,  Special  Method  for 71 

Gold  Alloys 147 

Assay  of,  Special 196 

Lead  for  Cupellation 155 

Gold    and   Silver,  Crucible  Assay 

Report 159 

and  Silver,  Preliminary  Assay 

of  Ores 66 

and  Silver,  Remarks  on 76 

and  Silver,  Roasting  of  Ores. .     67 
and    Silver,   Scorification    As- 
say. .  69 

and    Silver,  Scorification    As- 
say Report 160 

and  Silver,  Sources  of 64,  142, 

145,  146,  147 

Assay  of  Ores 64 

Bullion 115 

Bullion  Assay  Report 161 

Bullion,  Cupellation  for  Base 

Metal 115 

Bullion,  Parting 116 

Bullion,  Platinum   Apparatus 

for 118 

Bullion,  Remarks  on 117 

Crucible  Assay  for 65 

Determination  of,  by  Specific 

Gravity 195 

Multiplication  Table  for 154 

Ores 64,  143,  145,  146 

Ores,  Amalgamation  Assay. .  .   193 
Ores  and  Alloys,  Special   Me- 
thods    192 

Ores,  Fusion  of 68 

Ores,  Mechanical  Assay 192 

Purple  Cassius  Test  for 178 

Sulphurets,  Chlorination  Pro- 
cess   194 

Sweeps,  Assay  of 197 

Value  of  Pure 54,  141 

Weighing 75 

Grain  Weights,  Values  for 154 

Gravity,  Specific 150 

Specific,  Determination  of  Gold 

by 195 

Grinding  Plate 34 


H. 


Hardness,  Scale  of. 


139 


PAGE 

Ignition 174 

Inquartation 53,  74 

Introduction 13 

Iron,  Assay  for .'     94 

Crucible  Assay  Report 158 

Metallic 42 

Ores ..94  144 

Remarks  on 98,  132 

Scheme    for   Volumetric    As- 
say   131 

Sources  of 94,  144 


Kandelhardt.    Proportions  of  Lead 

for  Cupelling  Gold  Alloys. .   155 


Laboratory  Desk 36 

Lead,  Assay  for 57 

Button 71 

for  Cupelling  Gold  Alloys 155 

Ores 57,  142 

Pure 43 

Remarks  on. 60,  120 

Scheme  for 120 

Sources  of 57,  142 

Lime 44 

Powdered 44 

Lining  for  Crucibles 32 

Liquid  Measure,  French 149 

Measure,  United  States 149 

Litharge 40 

Lutes,  Cements  and  Washes 31 

Good  Fire 31 

Sundry 31 


M. 

Manipulation,  etc 173 

Manganese  Ores 133,  144 

Remarks  on 133 

Scheme  for 132 

Sources  of 133,  144 

Measure.  Cubic,  English 150 

Cubic,  French 150 

Liquid,  French 149 

Liquid,  United  States 149 

of  Weight  and  Volume 148 

Mechanical  Assay  of  Gold  Ores. .  .   193 

Mercury,  Assay  for 83 

Ores 83,  143 

Remarks  on 85 

Sources  of 83,  143 


208 


INDEX. 


PAGE 

Metallic  Iron 42 

Metals,  Characteristics 140 

Mine  Examination,  Rules  for 199 

Moulds,  Cupel 35 

Scorification 35 

Multiplication  Table  for  Gold 154 

N. 

Nickel,  Assay  for 99 

Cobalt  and  Copper,   Composi- 
tion of  Arsenides 101 

Determination  of,  in  the  Wet 

Way 134 

Ores 99,  144 

Remarks  on 101,  135 

Nickel,  Sources  of 99,  144 

Nitre ,     ....     43 

Normal  Salt  Solution 109 


0. 

Ores,  Antimony 61,  142 

Bismuth 85,  143 

Characteristics 142 

Cobalt 99,  144 

Copper 90,  143 

Gold 64,  142,  146,  147 

Iron 94,  144 

Lead 57,  142 

Manganese 133,  144 

Mercury 83,  143 

Nickel 99,  144 

Platinum 80,  142 

Preliminary  Assay  of 66 

Preliminary  Testing  of 45 

Relation  of  Weight  to  Volume.  147 

Silver 64,142,  145,  146 

Tin 86,  143 

Weighing 49 

Zinc 82,143 

Outfit,  Assayer's 191 

Outline  Examination  Scheme  for 

the  Assay  of  Ores . .  197 

P. 

Part   1 11 

II 55 

III 106 

IV  137 

Parting 52,  74,  116 

Flask  38 

Plate  for  Grinding 34 

Platinum  Apparatus  for  Gold  Bul- 
lion    118 

Assay  for 80 

Ores 80,142 


Platinum,  Remarks  on 81,  122 

Scheme  for 121 

Sources  of 80,  142 

Porcelain  Cap&ule 75 

Potassium,  Cyanide  of 41 

Ferro- Cyanide  of 41 

Powdered  Lime 44 

Precious  Stones.  Table  of 139 

Precipitants 44 

Precipitates,  Washing 174 

Precipitation 173 

Preliminary  Assay  of  Ores 66 

Assay  of  Silver  Bullion 110 

Testing  of  Ores 45 

Preparation   of    the  Normal   Salt 

Solution 109 

Problems  and  Questions 163 

Proportions  of  Lead  for  Cupelling 

1    Gold  Alloys 155 

Pulverizing 46 

Pure  Lead , 43 

Gold,  Value  of 54,  141 

Purple  Cassius  Test  for  Gold. ....  178 

Q. 

Qualitative    Analysis,     Zettnow's 

Scheme 204 

Quantitative  Report 156 

Questions  and  Problems  163 


Reagents  and  Chemicals 39 

and  Ores,  Weighing 49 

Blowpipe 186 

Chemical 189 

Extra 190 

Reduction  and  Fusion 51 

References  and  Tables 137 

on  Assaying 169 

Relation  of  Weight  to  Volume,  Ores  147 

Report,  Base  Metal  Assay 157 

General  Style  of 155 

Gold  Bullion 161 

Iron  Assay 158 

Quantitative 156 

Silver  and  Gold  Assay 159 

Silver  and  Gold  Scorification 

Assay 160 

Silver  Bullion 162 

Reporting 53 

Results,  Calculation  of 75 

Tabulating 53 

Roasting  and  Calcination 50 

Dishes 29 

of  Gold  and  Silver  Ores 67 


INDEX. 


209 


Rules  for  the   Examination  of  a 

Mine  .  .  .199 


S. 

Salt . 44 

Preparation  of  Normal 109 

Sampler 36 

Sampling 46 

Scale  of  Hardness 139 

Scheme  for  Blowpipe  Analysis.  . .   180 

for  Copper 128 

for  Lead 120 

for  Manganese 133 

for  Platinum 121 

for  Qualitative  Analysis 204 

for  Sulphur 135 

Scheme  for  Volumetric  Assay  for 

Iron 131 

for  Zinc 122 

of  Examination  for  the  Assay 

of  Ores 197 

Scorification 52,  69 

Assay,  Fluxes  for 69 

Assay,    Silver   and  Gold   Re- 
port    160 

Moulds 35 

Tongs 33 

Scorifiers 29 

Scraper 33 

Sieve,  Box 35 

Silica 41 

Silver  Alloys   146 

and  Gold  Crucible  Assay  Re- 
port     159 

and  Gold,  Roasting  of  Ores. . .     67 
and  Gold    Scorification  Assay 

Report 160 

Assay  of  Ores 64 

Bullion 109 

Bullion,  Apparatus  for 112 

Bullion,  Assay  Proper Ill 

Bullion,  Assay  Report 162 

Bullion,  Corrections  for  Cupel- 

lation Ill 

Bullion,     Preliminary     Assay 

of 110 

Bullion,  Remarks  on 113 

Crucible,  Assay  for 65 

Ores 64,  142,  145,  146 

Ores,  Fusion  of 68 

Remarks  on 76 

Sources  of 64,  142,  145,  146 

Soda,  Bi-Carbonate  of 40 

Solvents   44 

Sources  of  Antimony 61,  142 

of  Bismuth 85,  143 


Sources  of  Carbon 102,  145 

of  Cobalt 99,  144 

of  Copper 90,  143 

of  Gold 64,  142,  146,  147 

of  Iron 94,  144 

of  Lead 57 

of  Manganese 133,  144 

of  Mercury 83,  143 

of  Nickel 99,  144 

of  Platinum 80,  142 

of  Silver 64,  142,  145,  146 

of  Sulphur 135,  145 

of  Tin 86,  143 

of  Zinc 82,  143 

Special  Method  for  Galena 71 

Methods  for  Gold  Ores  and  Al- 
loys    192 

Specific  Gravity 150 

Determination  of  Gold  by  ....   195 

Starch 42 

Stones,  Precious 139 

Style  of  Report.  General 155 

Sublimation  and  Distillation 51 

Sulphur,  Remarks  on 136 

Scheme  for. .. 135 

Sources  of 135,  145 

Sulphurets,      Gold,      Chlorination 

Process  for 194 

Sulphurizing  Agents 44 

Sweeps,  Gold,  Assay  of 197 


T. 

Tables  and  References 137 

Tabulating  Results 53 

Tellurides 78 

Blowpipe  Test  for 179 

Test,  Blowpipe,  for  Tellurides  ...   179 

for  Gold,  Purple  Cassius 178 

Thermometers 1 53 

Tin,  Assay  for 87 

Determination  of,  in  the  Wet 

Way 125 

Ores 86,  143 

Remarks  on 90,  128 

Sources  of 86,  143 

Tongs,  Crucible,  etc 32 

Tools 32 

Touch-stone  Assay  of  Alloys 194 

Troy  Weights 148 


U. 


United  States,  Coins  of 148 

Liquid  Measure 149 

Units,  Comparison  of 150 


210 


INDEX. 


V. 

PAGE 

Value  of  Pure  Gold 54,  141 

Values  for  Grain  Weights 154 

Volume    and    Weight,    Measures 

of 148 

to  Weight,  Relation  of,  Ores. .   147 
Volumetric  Assay  for  Iron 131 

W. 

Wash  for  Crucibles 32 

for  Scorifiers 32 

Washes,  Lutes,  and  Cements 31 

Washing  Precipitates 174 

Weighing  Beads  and  Bullion. ..  52,  74 

Gold 75 

Ores  and  Reagents 49 

Weight    and    Volume,    Measures 
of .  148 


Weight  to  Volume,  Relation  of,  Ores  147 

Weights  and  Balances 18 

Assay 20,  149 

Atomic 14 

Avoirdupois 148 

French 149 

Grain,  Values  for 154 

Troy 148 

Wet  Assays 106 

Z. 

Zettnow's  Scheme  for  Qualitative 

Analysis 204 

Zinc,  Assay  for 82 

Ores 82,  143 

Remarks  on 83,  124 

Scheme  for 122 

Sources  of 82,  143 


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